A YAC library enriched for telomere clones was constructed and screened for the human telomere-specific repeat sequence (TTAGGG). Altogether 196 TYAC library clones were studied: 189 new TYAC clones were isolated, 149 STSs were developed for 132 different TY-ACs, and 39 P1 clones were identified using 19 STSs from 16 of the TYACs. A combination of mapping methods including fluorescence in situ hybridization, somatic cell hybrid panels, clamped homogeneous electric fields, meiotic linkage, and BLASTN sequence analysis was utilized to characterize the resource. Forty-five of the TYACs map to 31 specific telomere regions. Twenty-four linkage markers were developed and mapped within 14 proterminal regions (12 telomeres and 2 terminal bands). The polymorphic markers include 12 microsatellites for 10 telomeres (1q, 2p, 6q, 7q, 10p, 10q, 13q, 14q, 18p, 22q) and the terminal bands of 11q and 12p. Twelve RFLP markers were identified and meiotically mapped to the telomeres of 2q, 7q, 8p, and 14q. Chromosome-specific STSs for 27 telomeres were identified from the 196 TYACs. More than 30,000 nucleotides derived from the TYAC vector-insert junction regions or from regions flanking TYAC microsatellites were compared to reported sequences using BLASTN. In addition to identifying homology with previously reported telomere sequences and human repeat elements, gene sequences and a number of ESTs were found to be highly homologous to the TYAC sequences. These genes include human coagulation factor V (F5), Weel protein tyrosine kinase (WEE1), neurotropic protein tyrosine kinase type 2 (NTRE2), glutathione S-transferase (GST1), and beta tubulin (TUBB). The TYAC/P1 resource, derivative STSs, and polymorphisms constitute an enabling resource to further studies of telomere structure and function and a means for physical and genetic map integration and closure.Close

Phylogenetic divergence of the members of the Pongidae family has been based on genetic evidence. The terminal repeat array (T2AG3) has lately been considered as an additional basis to analyze genomes of highly related species. The recent isolation of subtelomeric DNA probes specific for human (HSA) chromosomes 7q and 14q has prompted us to cross-hybridize them to the chromosomes of the chimpanzee (PTR), gorilla (GGO) and orangutan (PPY) to search for its equivalent locations in the great ape species. Both probes hybridized to the equivalent telomeric sites of the long (q) arms of all three great ape species. Hybridization signals to the 7q subtelomeric DNA sequence probe were observed at the telomeres of HSA 7q, PTR 6q, GGO 6q and PPY 10q, while hybridization signals to the 14q subtelomeric DNA sequence probe were observed at the telomeres of HSA 14q, PTR 15q, GGO 18q and PPY 15q. No hybridization signals to the chromosome 7-specific alpha satellite DNA probe on the centromeric regions of the ape chromosomes were observed. Our observations demonstrate sequence homology of the subtelomeric repeat families D7S427 and D14S308 in the ape chromosomes. An analogous number of subtelomeric repeat units exists in these chromosomes and has been preserved through the course of differentiation of the hominoid species. Our investigation also suggests a difference in the number of alpha satellite DNA repeat units in the equivalent ape chromosomes, possibly derived from interchromosomal transfers and subsequent amplification of ancestral alpha satellite sequences.Close

We report on a 28-year-old man with trisomy 7q34-qter and monosomy 15q26.3-qter caused by a paternal balanced chromosomal translocation, t(7;15)(q34;q26.3). He had bilateral congenital glaucoma (buphthalmos), as well as typical manifestations of partial trisomy 7q. To our knowledge, this is the second description of a possible relation between congenital glaucoma and 7q trisomy. He also had some Silver-Russell syndrome features, such as short stature of prenatal onset, a characteristic triangular face, clinodactyly of the fifth fingers, and body asymmetry. Fluorescence in situ hybridization analysis on his chromosomes revealed that one copy of the insulin-like growth factor 1 receptor gene (IGF1R) at 15q25-q26 was deleted, suggesting a possible role of IGF1R in the SRS phenotype.Close

Four new cases of holoprosencephaly are described in fetuses exhibiting abnormal karyotypes with different distal and proximal rearrangements of the long arm of chromosome 7. Three of them showed terminal deletions of chromosome 7q, confirming the importance of the 7q36 region in holoprosencephaly. The karyotype of the fourth fetus showed an apparently balanced de novo translocation, t(7;13) (q21.2;q33), without any visible loss of the distal part of chromosome 7q. The involvement of new genes, different from the human Sonic Hedgehog gene (hShh) responsible for holoprosencephaly, or a positional effect are discussed.Close

We describe the combined use of comparative genomic hybridization (CGH) and fluorecence in situ hybridization (FISH) to identify the origin of de novo unbalanced translocations in a fetus with abnormalities on ultrasound examination and in a newborn with multiple congenital abnormalities. RHG banding of amniocytes and lymphocytes respectively showed a unbalanced karyotype: 46,XX,add(4)(q34), with normal parental karyotypes in both cases. CGH revealed a gain of material from distal 15q (q23qter) in the fetus and a gain of distal 7q (q31qter) in the newborn. CGH results were confirmed using FISH with painting probes in both cases. These cases demonstrate the efficiency of CGH in identifying the chromosomal origin of extramaterial in unbalanced de novo translocations.Close

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We report the prenatal diagnosis of partial trisomy 3p(3p23-->pter) and monosomy 7q(7q36-->qter) in a fetus with microcephaly, alobar holoprosencephaly and cyclopia. A 26-year-old primigravida woman was referred for genetic counselling at 23 gestational weeks due to sonographic findings of intra-uterine growth retardation and cranio-facial abnormalities. Level II ultrasonograms further demonstrated alobar holoprosencephaly, a proboscis above the eye and a single median orbit consistent with cyclopia. Genetic analysis and fluorescence in situ hybridization on cells obtained from amniocentesis showed distal 3p trisomy (3p23-->pter) and 7q36 deletion, 46,XX,der(7)t(3;7)(p23;q36), resulting from a paternal t(3;7) reciprocal translocation. The pregnancy was terminated. Autopsy further confirmed the presence of arrhinencephaly, agenesis of the corpus callosum and a single ventricle of the brain. The phenotype of this antenatally diagnosed case is compared with those observed in 10 previously reported cases with simultaneous occurrence of partial trisomy 3p and terminal deletion 7q. All cases are associated with severe forms of holoprosencephaly and facial dysmorphism. This delineates an autosomal imbalance syndrome or a dosage effect involving duplication of distal 3p/deficiency of terminal 7q and dysmorphogenesis of the forebrain and mid-face.Close

Human chromosomes terminate with specialized telomeric structures including the simple tandem repeat (TTAGGG)n and additional complex subtelomeric repeats. Unique sequence DNA for each telomere is located 100-300 kilobases (kb) from the end of most chromosomes. A high concentration of genes and a number of candidate genes for recognizable syndromes are known to be present in telomeric regions. The human telomeric regions represent a major diagnostic challenge in clinical cytogenetics, because most of the terminal bands are G negative, and cryptic deletions and translocations in the telomeric regions are therefore difficult to detect by conventional cytogenetic methods. In fact, several submicroscopic chromosomal abnormalities in patients with undiagnosed mental retardation or multiple congenital anomalies have been identified by other molecular methods such as DNA polymorphism analysis. To improve the sensitivity for deletion detection and to determine whether such cryptic rearrangements represent a significant source of human pathology that has not been previously appreciated, it would be valuable to have specific FISH probes for all human telomeres. We report here the isolation and characterization of a complete set of specific FISH probes representing each human telomere. As most of these clones are at a known distance of within 100-300 kb from the end of the chromosome arm, this provides a 10-fold improvement in deletion detection sensitivity compared with high-resolution cytogenetics (2-3 Mb resolution). While testing these probes, we serendipitously identified a family with multiple members carrying a cryptic 1q;11p rearrangement in the balanced or unbalanced state.Close

The 240-kb yeast artificial chromosome (YAC) HTY146 (D7S427) containing the telomere from the q arm of human chromosome 7 was subcloned into the cosmid vector sCOS-1. Cosmid subclones were screened for DNA polymorphisms by Southern blot analysis of restriction digests of DNA from random individuals. Four distinct polymorphisms were characterized. These markers provide a resource for defining the end of the genetic map for the long arm of human chromosome 7.Close

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Terminal deletion of 7q presents with variable anatomical and developmental findings. This case is the first reported in utero diagnosis based on cytogenetic findings and in utero demonstration of resolving congestive heart failure due to a truncus arteriosus.Close

We report 3 patients with a 7q terminal deletion. The first, a 7 weeks old female, with a de novo 7q36-->qter deletion, was microcephalic and had a partial hypoplasia of the corpus callosum on the MRI-scan of the brain. The second, a 3 months old male, showed microcephaly, disproportionate growth retardation, truncal obesity and facial dysmorfism giving the clinical impression of a "microcephalic primordial dwarfism (osteodysplastic type)". At the age of 6 months he had developed a single maxillary central incisor suggesting a minimal form of holoprosencephaly (HPE). Additional FISH-studies showed a 7q36.1-->qter deletion, as the unbalanced product of a t(5;7)(q35.2;q36.1)pat. The de novo 7q36-->qter deletion in the third patient, a 5 years old female, was associated with borderline intelligence, mild microcephaly, small midface, choanal narrowing and a single maxillary central incisor as a minimal form of HPE. CT- and MRI-scan of the brain were normal. In these 3 patients extensive FISH analysis was performed to investigate the possible involvement of the HPE gene region on chromosome 7q36. The target gene for HPE, the Sonic hedgehog gene (SHH) as well as several other genes important for normal brain development (En2;HOX1,HTR5A) were found to be deleted in all three patients. Our findings stress the importance of 7q36 microdeletion studies in patients with even minimal signs of HPE, as relative microcephaly with small midface (choanal narrowing), agenesis/hypoplasia of the corpus callosum/septum pellucidum, thalamic fusion or a single maxillary central incisor.Close

We report on a de novo 7q36 deletion in a 3-month-old girl with manifestations of the 7q terminal deletion syndrome. Only minimal findings of holoprosencephaly (HPE) were present since only a partial corpus callosum hypoplasia was seen on a magnetic resonance imaging scan of the brain. Extensive fluorescence in situ hybridization analysis showed that the HPE3 critical gene region, inclusive Sonic hedgehog (SHH), En2 (HOX1), and HTR5A, was deleted. A review of 33 other patients with a de novo terminal 7q deletion and the different types of HPE manifestations within these patients will be presented.Close

A familial balanced t(7;9) (q36;q34) was reported recently. Analysis of the craniofacial features of 3 of the sibs showed signs of holoprosencephaly. Two of the sibs have an unbalanced derivative chromosome leading to del(7) (q36) and dup(9) (q34), while the other has a cytogenetically balanced translocation. These findings, together with several reports associating holoprosencephaly with terminal 7q deletions, indicate that a putative locus for holoprosencephaly resides at or near 7q36. It should now be feasible to clone this locus.Close

We have constructed a 2.4-cM resolution genetic linkage map for chromosome 7q that is bounded by centromere and telomere polymorphisms and contains 66 loci (88 polymorphic systems), 38 of which are uniquely placed with odds for order of at least 1000:1. Ten genes are included in the map and 11 markers have heterozygosities of at least 70%. This map is the first to incorporate several highly informative markers derived from a telomere YAC clone HTY146 (locus D7S427), including HTY146c3 (HET 92%). The telomere locus markers span at least 200 kb of the 7q terminus and no crossovers within the physical confines of the locus were observed in approximately 240 jointly informative meioses. The sex-equal map length is 158 cM and the largest genetic interval between uniquely localized markers in this map is 11 cM. The female and male map lengths are 181 and 133 cM, respectively. The map is based on the CEPH reference pedigrees and includes over 4000 new genotypes, our previously reported data plus 29 allele systems from the published CEPH version 5 database, and was constructed using the program package CRI-MAP. This genetic linkage map can be considered a baseline map for 7q, and will be useful for defining the extent of chromosome deletions previously reported for breast and prostate cancers, for developing additional genetic maps such as index marker and 1-cM maps, and ultimately for developing a fully integrated genetic and physical map for this chromosome.Close

Triphalangeal thumb is a developmental anomaly, sometimes dominantly transmitted, characterized by a long, finger-like thumb with three phalanges instead of two. The underlying genetic defect is unknown, but presumably involves genes that regulate the differentiation of the developing forelimb. In two large kindreds with triphalangeal thumb, evidence for linkage to the long arm of chromosome 7 was obtained with a maximum lod score of 12.61. Multipoint linkage and haplotype analysis placed the gene close to the telomere of the long arm. To our knowledge this is the first time that a human gene involved solely in the pathologic morphogenesis of the hand and feet has been localized.Close

The molecular basis of a highly polymorphic RFLP marker, HTY146c3 (D7S591), within the subtelomeric region of human chromosome 7q was determined by restriction-fragment and DNA sequence analysis. Two polymorphic systems were found--a simple base-substitution polymorphism and a GC-rich VNTR element with a core structure of C3AG2C2. In addition, a compound-imperfect CA dinucleotide-repeat element was identified approximately 10-20 kb from the telomeric sequence repeat (T2AG3), demonstrating that microsatellites can extend essentially to the ends of human chromosomes. The microsatellite marker, sAVH-6 (D7S594), is highly polymorphic, with 10 alleles and an observed heterozygosity of 84% found with the CEPH (Centre d'Etude du Polymorphisme Humain) reference pedigree collection. In combination with the RFLPs, the informativeness of the markers contained within 240 kb at the telomere approaches 100%. A unique genetic and physical STS marker, sAVH-6, defines the endpoint of the long arm of human chromosome 7.Close

We have characterized a 6-generation North American Caucasian kindred segregating one form of preaxial polydactyly type 2 (PPD-2). We demonstrate linkage to the 7q36 region and describe a submicroscopic telomeric chromosomal deletion in phase with the PPD-2 phenotype. Recently, several kindreds segregating triphalangeal thumb (TPT) with and without associated hand anomalies (syndactyly and/or postaxial polydactyly) have also been linked to the subtelomeric region of chromosome 7q [Heutink et al., 1994: Nat Genet 6:287-291; Tsukurov et al., 1994: Nat Genet 6:282-286]. We demonstrate by haplotype analysis that our North American pedigree represents a PPD allele that is independent of the founder PPD allele present in the previously described kindreds.Close

We report a rare case of duplication for 7q22 --> 7qter and deletion for 7p22 --> 7pter, resulting from a meiotic recombination of a paternal pericentric inversion, inv(7)(p22q22). The newborn boy had the 7q trisomy syndrome. In addition, the diagnosis of chondrodysplasia punctata was made from lumbar and hand X-ray films taken soon after birth. Only two cases of rec(7)dup(7q), both in a single family, have been reported previously. We review 133 offspring with recombinations resulting from pericentric inversions on any chromosomes reported between 1981 and 1995. Of the 133 cases, 110 had a long-arm duplication and short-arm deletion, while only 23 had a short-arm duplication and long-arm deletion. In 85 of the 133 cases, the mother was an inversion carrier (five carriers had two affected offspring), and in 46, the carrier was a father (one carrier had three affected offspring). Kaiser [Hum Genet 1984;68:1-47] reviewed 63 offspring with recombinations derived from a parental pericentric inversion reported between 1972 and 1981. In both surveys, recombinations resulting from pericentric inversions of chromosomes 1, 12, 19, and Y were not found.Close

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Telomere-specific clones are a valuable resource for the characterization of chromosomal rearrangements. We previously reported a first-generation set of human telomere probes consisting of 34 genomic clones, which were a known distance from the end of the chromosome ( approximately 300 kb), and 7 clones corresponding to the most distal markers on the integrated genetic/physical map (1p, 5p, 6p, 9p, 12p, 15q, and 20q). Subsequently, this resource has been optimized and completed: the size of the genomic clones has been expanded to a target size of 100-200 kb, which is optimal for use in genome-scanning methodologies, and additional probes for the remaining seven telomeres have been identified. For each clone we give an associated mapped sequence-tagged site and provide distances from the telomere estimated using a combination of fiberFISH, interphase FISH, sequence analysis, and radiation-hybrid mapping. This updated set of telomeric clones is an invaluable resource for clinical diagnosis and represents an important contribution to genetic and physical mapping efforts aimed at telomeric regions.Close

We describe a subtle familial chromosome rearrangement which involves 7q36 and 9q34. The clinical manifestations of 3 apparently balanced individuals with presumed identical translocation breakpoints are presented. In addition, the phenotypes of 2 cytogenetically unbalanced sibs in the same nuclear family are compared.Close

At least nine cases of holoprosencephaly (HPE) found in patients with confirmed loss of 7q34—-7qter or 7q36—-7qter have been reported in the literature. In the present report, balanced rearrangements involving chromosome 7q [inv(7)(p22.1q34) and t(4;7)(q31;q36)] were shown in two mothers examined after the birth of their non-karyotyped infants with HPE and hydronephrosis. In both cases, del(7q) was the most probable imbalance. The available data confirm the association between HPE and del(7q). Predominance of cyclopia and cebocephaly, the severest forms of HPE, suggests that del(7q) may be an important factor in arresting prosencephalon development at the earliest stages.Close

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Two unrelated cases of single maxillary central incisor (SM-CI) with 7q terminal deletion of the same breakpoint at 7q36.1 were described. They had mental retardation, microcephaly, hypotelorism, short stature, and normal levels of plasma growth hormone. One case had bilateral caudal ectopic kidneys, double renal pelves, and dilated ureters. The other had bilateral hydroureteronephrosis. The present cases suggest that 7q terminal deletion is one of the causes of SMCI.Close

We describe a de novo terminal deletion of the long arm of chromosome 7 in a 5 year old girl with the Currarino triad, characterised by congenital anorectal stenosis, a sacral defect, and a presacral mass. Recently, this autosomal dominant trait has been shown to be linked to 7q36, the same region as holoprosencephaly (HPE3). The cytogenetic findings in the present patient with the Currarino triad provided further evidence that a gene(s) for the Currarino triad is located in the 7 q terminal segment.Close

We describe here a fetus with holoprosencephaly and signs of caudal deficiency sequence. Chromosome examination showed a de novo balanced reciprocal translocation (7;22) (q36;q11) with loss of the derivative chromosome 22 in 50% of the cells examined. The present report and available published data indicate that the terminal region of the long arm of chromosome 7 contains genes implicated in the development of the central nervous system and the caudal region.Close

We describe a child with multiple anomalies and severe retardation with dup 7pter-p15.1 and del 7q36-qter as a result of a parental pericentric inversion of chromosome 7. The pericentric inversion was found in family members in 3 generations with 9 liveborn children who had severe anomalies probably associated with imbalances of chromosome 7.Close

Unbalanced submicroscopic subtelomeric chromosomal rearrangements represent a significant cause of unexplained moderate to severe mental retardation with and without phenotypic abnormalities. We investigated 254 patients (102 from Zurich, 152 from Liege) for unbalanced subtelomeric rearrangements by using fluorescence in situ hybridisation with probes mapping to 41 subtelomeric regions. Mental retardation combined with a pattern of dysmorphic features, with or without major malformations, and growth retardation and a normal karyotype by conventional G-banding were the criteria of inclusion. Selection criteria were more restrictive for the Zurich series in terms of clinical and cytogenetic pre-investigation. We found 13 unbalanced rearrangements and two further aberrations, which, following the investigation of other family members, had to be considered as variants without influence on the phenotype. The significant aberrations included three de novo deletions (two of 1pter, one of 5pter), three de novo duplications (8pter, 9pter, Xpter), one de novo deletion 13qter-duplication 4qter, and five familial submicroscopic translocations [(1q;18p), (2q;4p), (2p;7q), (3p;22q), (4q;10q), (12p;22q)], most of them with several unbalanced offspring with deletion-duplication. Although the incidence of abnormal results was higher (10/152) in the Liege versus the Zurich series (3/102), similar selection criteria in Zurich as in Liege would have resulted in an incidence of 7/106 and thus similar figures. In our series, submicroscopic unbalanced rearrangements explain the phenotype in 13/254 study probands. The most important selection criterion seems to be the presence of more than one affected member in a family. An examination of subtelomeric segments should be included in the diagnostic work-up of patients with unexplained mental retardation combined with physical abnormalities, when a careful conventional examination of banded chromosomes has yielded a normal result and a thorough clinical examination does not lead to another classification. The proportion of abnormal findings depends strongly on selection criteria: more stringent selection can eliminate some examinations but necessitates a high workload for experienced clinical geneticists. Once the costs and workload of screening are reduced, less selective approaches might finally be more cost-effective.Close

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DNA from a 240-kb human telomeric yeast artificial chromosome (HTY) clone was analyzed using physical mapping methods. Cosmid subclones of the YAC were fingerprinted using restriction enzyme digestion and human repeat sequence hybridization and then assembled into two contigs that together span 93% of the human insert. Data from restriction mapping and Bal31 exonuclease experiments indicate that, except for the truncation of distal genomic (T2AG3)n sequences, the molecular clone HTY 146 contains a contiguous, 230-kb telomere-terminal fragment from 7qter. Markers derived from this clone will allow telomeric closure of the physical and genetic linkage maps of human chromosome 7q.Close

A ring chromosome 7 was found in a 19-month-old girl with microcephaly, growth and developmental delay, multiple angiomas, and partial sacral agenesis. Absent sacrum is a frequent finding in patients with 7q terminal deletions; in fact, genes involved in the sacral agenesis are localized in 7q36. However, this anomaly was not described previously in patients with a ring chromosome 7. High resolution G-banding chromosome and fluorescence in situ hybridization (FISH) demonstrated that our patient lost this region during ring formation.Close

Holoprosencephaly (HPE) is a genetically heterogeneous disorder that affects the midline development of the forebrain and midface in humans. As a step toward identifying one of the HPE genes, we have set out to refine the HPE3 critical region on human chromosome 7q36 by analyzing 34 cell lines from families with cytogenetic abnormalities involving 7q, 24 of which are associated with HPE. Genomic clones surrounding the DNA marker D7S104, which has previously been shown to be in the HPE3 critical region, have been examined by fluorescent in situ hybridization and microsatellite analysis of our panel of patient cell lines. We report the analysis of a cluster of four translocation breakpoints within a 300-kb region of 7q36 that serves to define the minimal critical region for HPE3 and that has directed the search for candidate genes. The human Sonic Hedgehog (hSHH) gene maps to this region and has been shown to be HPE3 on the basis of mutations within the coding region of the gene. We present evidence that cytogenetic deletions and/or rearrangements of this region of chromosome 7q containing Sonic Hedgehog, and translocations that may suppress Sonic Hedgehog gene expression through a position effect are common mechanisms leading to HPE.Close

Phylogenetic divergence of the members of the Pongidae family has been based on genetic evidence. The terminal repeat array (T2AG3) has lately been considered as an additional basis to analyze genomes of highly related species. The recent isolation of subtelomeric DNA probes specific for human (HSA) chromosomes 7q and 14q has prompted us to cross-hybridize them to the chromosomes of the chimpanzee (PTR), gorilla (GGO) and orangutan (PPY) to search for its equivalent locations in the great ape species. Both probes hybridized to the equivalent telomeric sites of the long (q) arms of all three great ape species. Hybridization signals to the 7q subtelomeric DNA sequence probe were observed at the telomeres of HSA 7q, PTR 6q, GGO 6q and PPY 10q, while hybridization signals to the 14q subtelomeric DNA sequence probe were observed at the telomeres of HSA 14q, PTR 15q, GGO 18q and PPY 15q. No hybridization signals to the chromosome 7-specific alpha satellite DNA probe on the centromeric regions of the ape chromosomes were observed. Our observations demonstrate sequence homology of the subtelomeric repeat families D7S427 and D14S308 in the ape chromosomes. An analogous number of subtelomeric repeat units exists in these chromosomes and has been preserved through the course of differentiation of the hominoid species. Our investigation also suggests a difference in the number of alpha satellite DNA repeat units in the equivalent ape chromosomes, possibly derived from interchromosomal transfers and subsequent amplification of ancestral alpha satellite sequences.Close

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A fetus with severe sacral agenesis and intrauterine growth retardation, ascertained at prenatal diagnosis, was found to be carrying an unbalanced form of a paternal balanced reciprocal translocation (7;19)(q36.1;q13.43), resulting in functional monosomy for 7q36.1-->qter. Necropsy confirmed that the fetus had isolated sacral agenesis type II. A critical region for autosomal dominant sacral agenesis has recently been mapped to the 7q36 region. This case provides further evidence for a sacral agenesis locus in this region and may help to refine the critical region further.Close

We report on a patient with ring chromosome 7 analyzed by both high-resolution mid-prophase G-banding and fluorescence in situ hybridization (FISH) resolving a subband deletion of 7q36.3 associated with the clinical manifestation of holoprosencephaly (HPE).Close

We report a family in which the proband has a direct insertion of band 7q21.3 into chromosome 22 at 22q13.3, karyotype 46,XX,dir ins(22;7)(q13.3;q21.2q22.1). Two of her children have unbalanced chromosome rearrangements involving 7q21.3, with one girl monosomic for the region and a boy trisomic for the region. The child monosomic for band 7q21.3 has a split hand/split foot (SHSF) anomaly and her clinical features are consistent with the 7q21-q22 contiguous gene deletion syndrome. In situ hybridisation studies have shown that the proband and her son have a submicroscopic deletion of chromosome band 22q13.3. Interstitial deletions of this chromosome band have rarely been reported.Close

Few patients with trisomy of the most distal region of chromosome 7q have been described. We report on a familial translocation t(2;7)(q37;q35) leading to trisomy 7q35-->7qter in a child and her paternal uncle and a minimal deletion of distal 2q as demonstrated by FISH with probes located in the chromosome 2q subtelomeric region. The clinical phenotype included macrocephaly and low-set ears, also found in other reported patients trisomic for the distal part of chromosome 7q. Phenotypic findings probably useful for the clinical diagnosis include normal size at birth, large head with frontal bossing, low-set ears of normal shape, small nose and low nasal bridge, feeding difficulties in infancy, and severe neurodevelopmental delay.Close

We report a 34-year-old female with a de novo balanced reciprocal translocation involving 2q37.2 and 7q36.3. She has a unique combination of multiple congenital malformations that include redundant skin, complete tissue syndactyly of the hands and feet, hirsutism, polycystic ovaries and bilateral anterior chamber eye anomalies. Her son has inherited the unbalanced product (46,XY,der(2) t(2;7)(q37.2;q36.3). He has a similar clinical picture with additional features including complex congenital heart disease, post axial polydactyly, hypotonia and global developmental delay. The breakpoints may indicate the location of the gene(s) responsible for this unique combination of features.Close

We demonstrated that the gene responsible for a congenital limb deformity (polysyndactyly) maps to chromosome 7q36 in a large family. Pre- and postaxial anomalies of the extremities are inherited in this family as an autosomal dominant trait. The disease locus is closely linked to D7S550 (maximum lod score = 6.85, theta = 0). This region is homologous to a segment of mouse chromosome 5, where the mutations hammer toe (HM) and hemimelic extra toes (HX) have been mapped. These data suggest that human chromosome 7q36 and the homologous region of mouse chromosome 5 contain genes involved in limb pattern formation.Close

The holoprosencephaly (HPE) sequence is a malformation complex with abnormal midline cleavage of the embryonic forebrain. HPE is genetically heterogeneous with at least 6 different chromosome regions containing genes involved in the expression of the phenotype. HPE3, recently identified as the human Sonic hedgehog gene, is localized to 7q36. We have used fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR) amplification in 5 cell lines from patients with HPE (3 cases), HPE and sacral agenesis (1 case), and microcephaly (1 case) to further define the structural rearrangements of the long arm of chromosome 7 in each case. All cell lines demonstrated loss of material in the critical region of HPE3 at band 7q36, which includes the Sonic hedgehog gene. We report here the analysis of these patient cell lines.Close

We have developed a strategy for the isolation of terminal deletion breakpoints from any chromosome that has been healed by de novo addition of a telomere repeat array. Breakpoints at 7q32 and 22q13.3 have been isolated and characterized in two patients (patients FB336R and AJ). Both truncated chromosomes have been healed by the addition of a novel telomere, with such an addition possibly mediated by the enzyme telomerase. The breakpoint at 7q32 in patient FB336R shows a structure similar to that of breakpoints on other chromosomes that have been healed in this way. However, the breakpoint at 22q13.3 in patient AJ has 10 nucleotides of unknown origin inserted between the sequence unique to chromosome 22q and the start of the telomere repeat array. This unusual structure is suggestive of a multistep healing event resulting in de novo telomere addition at this breakpoint, and possible mechanisms are discussed.Close

We report on a new case of a single band duplication of the long arm of chromosome 7, dir dup (7)(q36—-qter). The major manifestations are developmental delay (particularly speech), frontal bossing, macrocrania, and constant drooling. When compared with other cases involving a 7q duplication of various segments, our patient has a few minor anomalies. This case illustrates the genotype/phenotype correlation in a child with a single band duplication which has resulted in duplication of 7q36—-qter. A tabulation of reported cases with duplication of various segments of 7q is provided, which may serve as an aid for clinicians.Close

Many cases of 7q deletion associated with mental retardation and multiple malformations have been described, nevertheless it is quite different to recognize common features among these infants. In this paper the cases of two female infants with uncommon facial features and 7q deletion are described. We also try to recognize the phenotypic features of this chromosomal disorder.Close

A YAC library enriched for telomere clones was constructed and screened for the human telomere-specific repeat sequence (TTAGGG). Altogether 196 TYAC library clones were studied: 189 new TYAC clones were isolated, 149 STSs were developed for 132 different TY-ACs, and 39 P1 clones were identified using 19 STSs from 16 of the TYACs. A combination of mapping methods including fluorescence in situ hybridization, somatic cell hybrid panels, clamped homogeneous electric fields, meiotic linkage, and BLASTN sequence analysis was utilized to characterize the resource. Forty-five of the TYACs map to 31 specific telomere regions. Twenty-four linkage markers were developed and mapped within 14 proterminal regions (12 telomeres and 2 terminal bands). The polymorphic markers include 12 microsatellites for 10 telomeres (1q, 2p, 6q, 7q, 10p, 10q, 13q, 14q, 18p, 22q) and the terminal bands of 11q and 12p. Twelve RFLP markers were identified and meiotically mapped to the telomeres of 2q, 7q, 8p, and 14q. Chromosome-specific STSs for 27 telomeres were identified from the 196 TYACs. More than 30,000 nucleotides derived from the TYAC vector-insert junction regions or from regions flanking TYAC microsatellites were compared to reported sequences using BLASTN. In addition to identifying homology with previously reported telomere sequences and human repeat elements, gene sequences and a number of ESTs were found to be highly homologous to the TYAC sequences. These genes include human coagulation factor V (F5), Weel protein tyrosine kinase (WEE1), neurotropic protein tyrosine kinase type 2 (NTRE2), glutathione S-transferase (GST1), and beta tubulin (TUBB). The TYAC/P1 resource, derivative STSs, and polymorphisms constitute an enabling resource to further studies of telomere structure and function and a means for physical and genetic map integration and closure.Close