Clinical and molecular characterisation of 80 patients with 5p deletion: genotype-phenotype correlation.

The majority of deletions of the short arm of chromosome 5 are associated with cri du chat syndrome (CdCS) and patients show phenotypic and cytogenetic variability. To perform a genotype-phenotype correlation, 80 patients from the Italian CdCS Register were analysed. Molecular cytogenetic analysis showed that 62 patients (77.50%) had a 5p terminal deletion characterised by breakpoint intervals ranging from p13 (D5S763) to p15.2 (D5S18). Seven patients (8.75%) had a 5p interstitial deletion, four (5%) a de novo translocation, and three (3.75%) a familial translocation. Of the remaining four patients, three (3.75%) had de novo 5p anomalies involving two rearranged cell lines and one (1.25%) had a 5p deletion originating from a paternal inversion. The origin of the deleted chromosome 5 was paternal in 55 out of 61 patients (90.2%). Genotype-phenotype correlation in 62 patients with terminal deletions highlighted a progressive severity of clinical manifestation and psychomotor retardation related to the size of the deletion. The analysis of seven patients with interstitial deletions and one with a small terminal deletion confirmed the existence of two critical regions, one for dysmorphism and mental retardation in p15.2 and the other for the cat cry in p15.3. Results from one patient permitted the cat cry region to be distally narrowed from D5S13 to D5S731. Furthermore, this study lends support to the hypothesis of a separate region in p15.3 for the speech delay.

Sequence and genomic organization of the human G-protein Golfalpha gene (GNAL) on chromosome 18p11, a susceptibility region for bipolar disorder and schizophrenia.

The sequence and genomic organization of the human Golfalpha (GNAL) gene were determined. The human GNAL gene was found to contain 12 coding exons, and it spans over 80 kb on chromosome 18p11. 5' RACE analysis suggested an additional transcription initiation start site. Sequence analysis of the putative promoter region revealed conserved binding sites for several transcription factors. Sequence analysis of the 3'-untranslated region revealed the presence of two Alu sequences and two polyadenylation signals. 3' RACE analysis confirmed the functionality of the most downstream poly-a signal. The human GNAL was found to be expressed as a single transcript of about 5.9 kb in the brain. One highly informative dinucleotide repeat was found in intron 5. Additionally, a processed pseudogene for asparagine synthetase was found about 6 kb upstream of the GNAL gene. Knowledge of the sequence and structure of the human GNAL gene provides essential information for further analysis of the GNAL locus at chromosome 18p11 which has been linked to bipolar disorder and schizophrenia.

Growth charts for cri-du-chat syndrome: an international collaborative study.

Low birth weight and slow growth are frequently observed in the patients with cri-du-chat syndrome. To provide a growth reference standard for children with cri-du-chat syndrome, syndrome-specific growth charts have been developed from a combination of cross-sectional and longitudinal measurements on 374 patients from North America, Italy, Australia, and the British Isles. The data were obtained from pediatric records, parent reporting, and personal examinations at national 5p- parent support group meetings in the U.S., Italy, U.K., and Australia. The growth curves include height and weight measurements for patients ages 0 to 18 years and head circumference measurements for patients ages 0 to 15 years. Birth weight was above the 5th percentile of general population in 50% of cases: mean weight 2.8 kg +/- 1.85 SD for males and 2.6 kg +/- 1.51 SD for females. Growth curve medians were usually at or below the 5th centile of reference populations throughout life. The median head circumference falls below the 2nd centile, and this change increases with age. The charts show that compared with the standard population, most children with cri-du-chat syndrome are small at birth and as they grow most, but not all, have significant microcephaly and compromised weight for age, and to a lesser extent, compromised height for age. Am. J. Med. Genet. 94:153-162, 2000.

Identification of candidate genes for psychiatric disorders on 18p11.

Linkage studies have suggested a locus for bipolar disorder as well as schizophrenia in the pericentric region of chromosome 18. Several candidate genes have been identified in the region including ACTH, IMP, and G(olf), however no reports of mutations in families showing linkage to the 18p11 locus have been reported. Recently, mild linkage disequilibrium has been observed with a polymorphic marker that maps within the G(olf) gene and schizophrenia in families from Germany and Israel, suggesting that a gene mapping near G(olf) may be involved in psychiatric disorders. A BAC and cosmid contig around the G(olf) locus has been generated and BAC clones were used for cDNA selection experiments. Several novel genes have been identified which are expressed in the brain. These genes may be possible candidate genes for psychiatric illness.

Hemizygosity of delta-catenin (CTNND2) is associated with severe mental retardation in cri-du-chat syndrome.

Delta-catenin is an adherens junction protein involved in cell motility and expressed early in neuronal development. It was discovered as an interactor with presenilin-1. The genomic structure of the human delta-catenin gene (Human Gene Nomenclature Committee-approved symbol CTNND2) was determined and mapped to 5p15.2. A deletion of this chromosomal region has been associated with the cri-du-chat syndrome (CDCS), a segmental aneusomy syndrome of 5p that is associated with an unusual high-pitched cry at birth, facial dysmorphology, poor growth, and severe mental retardation. delta-catenin maps to a specific region in 5p15.2 that has been implicated in the mental retardation phenotype. The breakpoints in patients with 5p terminal deletions were characterized with respect to the severity of mental retardation and the physical location of the delta-catenin gene. A strong correlation was found between the hemizygous loss of delta-catenin and severe mental retardation. These findings and the properties of delta-catenin as a neuronal-specific protein, expressed early in development and involved in cell motility, support its role in the mental retardation of CDCS when present in only one copy.

5p14 deletion associated with microcephaly and seizures.

We report on a father and son who have an interstitial deletion of 5p14. The father is clinically and mentally normal while the son has significant clinical involvement including microcephaly, seizures, and global developmental delay. The extent of the 5p14 deletion was determined using fluorescence in situ hybridisation (FISH). The deletion in this present family is smaller than a deletion previously described in a multigenerational family that lacks any clinical phenotype. This report shows that a 5p14 deletion does not always lead to a normal phenotype.

Physical map and characterization of transcripts in the candidate interval for familial chondrocalcinosis at chromosome 5p15.1.

The gene for familial chondrocalcinosis (MIM 118600; gene symbol CCAL2) has been localized to a 0.8-cM interval on the short arm of chromosome 5, between the polymorphic microsatellite markers D5S416 and D5S2114. We have undertaken the physical and transcript mapping of this interval, as well as regions telomeric to the interval, in an attempt to define ultimately the gene for this disorder. The physical map is composed of YAC, BAC, PAC, and cosmid resources and spans a physical distance of approximately 0.3 Mb. Using cDNA selection, we have identified eight novel transcripts in and around the interval; two of the selected transcripts reside in the candidate interval. We have also more precisely placed several expressed sequence tags (ESTs) that were previously mapped by radiation hybrid analysis and were reported to reside in or near the candidate interval. Two of the ESTs analyzed overlap with the selected cDNAs that reside in the candidate interval. All of the selected cDNAs are expressed partial transcripts, as determined by Northern blot analysis, and using RT-PCR analysis, we have determined that the cDNAs that reside in the candidate interval are expressed in cartilage and synovium, tissues that are presumably relevant to the chondrocalcinosis phenotype.

An integrated physical map for the short arm of human chromosome 5.

The short arm of human chromosome 5 contains approximately 48 Mb of DNA and comprises 1.5% of the genome. We have constructed a mega-YAC/ STS map of this region that includes 436 YACs anchored by 216 STSs. By combining and integrating our map with the 5p maps of other groups using the same recombinant DNA library, a comprehensive map was constructed that includes 552 YACs and 504 markers. The YAC map covers >94% of 5p in four YAC contigs, bridges the centromere, and includes an additional 5 Mb of 5q DNA. The average marker density is 95 kb. This integrated 5p map will serve as a resource for the continuing localization of genes on the short arm of human chromosome 5 and as a framework for both generating and aligning the DNA sequence of this region.

Exclusion of the gene for human cartilage intermediate layer protein in currently mapped calcium pyrophosphate dihydrate deposition syndromes.

OBJECTIVE: To map the gene for human cartilage intermediate layer protein (CILP) in order to assess its involvement in some familial forms of calcium pyrophosphate dihydrate (CPPD) deposition disease. METHODS: A radiation hybrid panel was analyzed for chromosomal assignment of the CILP gene within a 1-cM limit of resolution. The location of the gene for CILP was confirmed to reside at the observed radiation hybrid locus by fluorescence in situ hybridization. RESULTS: The human CILP gene resides at chromosome 15q21. CONCLUSION: This map location definitively excludes mutations in the CILP gene as the cause of certain familial forms of CPPD deposition disease that have been genetically mapped to chromosomes 8q and 5p.

Variability in a family with an insertion involving 5p.

Cri-du-chat syndrome is due to a partial deletion of the short arm of chromosome 5 and comprises a catlike cry, minor facial anomalies, growth delays, and psychomotor retardation. We identified a family with an insertion involving chromosome areas 5p and 16q. Four relatives are balanced carriers and have a normal phenotype, 5 have inherited the insertion in an unbalanced form with 2 resulting in partial trisomy of 5p and 3 in partial monosomy of 5p. The 3 individuals show a variable phenotype with respect to mental delay and some of the findings of cri-du-chat syndrome. The extent of the 5p deletion in this family was determined using previously mapped markers. The deletion in this family was informative for further refining the phenotypic map for the cri-du-chat syndrome. This family demonstrates the importance of performing phenotype-genotype correlation studies based on the presence rather than the absence of abnormalities.

Characterization of a complex chromosomal rearrangement in a patient with a typical catlike cry and no other clinical findings of cri-du-chat syndrome.

We report on the clinical, cytogenetic, and molecular cytogenetic findings in a 4-year-old girl who was evaluated for developmental delay and a catlike cry from birth. No other findings of cri-du-chat syndrome were present. Karyotype analysis demonstrated a de novo deletion and inverted duplication of the 5p region. The abnormality was confirmed and further defined by detailed FISH analysis using cosmid and lambda phage clones previously mapped to distinct regions of 5p. The analyses documented deletion of 5p15.3-->pter and an inverted duplication of 5p14-->5p15.3. The deleted segment on 5p contains the region implicated in the isolated catlike cry feature of the cri-du-chat syndrome, confirming that the genes involved in the catlike cry map to the distal end of 5p. Except for the catlike cry and possibly the developmental delay that may be due to the deletion of 5p, the duplication of 5p14-->5p15.3 in this patient did not present with additional anomalies. This study further demonstrates the usefulness of the molecular cytogenetic approach for characterizing complex chromosome rearrangements. Such analyses of patients with an isolated catlike cry can avoid an incorrect diagnosis of the cri-du-chat syndrome, which is associated with a more severe prognosis.

No relationship between the size of the deletion and the level of developmental delay in cri-du-chat syndrome.

Molecular cytogenetic and developmental assessment was performed on 50 individuals with cri-du-chat syndrome. Fluorescent in situ hybridization analysis was used to confirm a terminal deletion karyotype and map more precisely the location of the deletion breakpoint. We identified terminal deletion breakpoints mapping from 5p15.2 to 5p13. Developmental assessment was performed using the Vineland Adaptive Behavior Scales test. Composite Vineland Scores ranged from 20-75. In general, the communication score was higher than the composite score. Comparison of the size of the deletion with the composite Vineland score, as well as the Vineland Communication score, demonstrated that there was no correlation between the size of the deletion and the level of developmental delay. These results demonstrate that patients with cri-du-chat syndrome show high variability in the level of developmental achievement.

An 18q- syndrome breakpoint resides between the duplicated serpins SCCA1 and SCCA2 and arises via a cryptic rearrangement with satellite III DNA.

The 18q-syndrome is representative of a group of terminal deficiency or macrodeletion syndromes characterized by mental retardation and congenital malformations. To gain insight into the mechanism of chromosomal loss and stabilization in these disorders, we cloned a putative terminal deletion breakpoint from an 18q-syndrome patient. The 18q21.3 breakpoint occurred between two nearly identical serine protease inhibitor (serpin) genes, SCCA1 and SCCA2. Although cytogenetic studies suggested that this chromosomal aberration was formed by a simple terminal deletion, DNA sequence analysis, pulsed-field gel electrophoresis and fluorescence in situ hybridization showed that the breakpoint was contiguous with a 35 bp filler sequence followed by a satellite III DNA-containing telomeric fragment of 475-1000 kb. This type of satellite III DNA sequence was not detected on the normal chromosome 18, but was highly homologous with types of satellite III DNA sequences normally located on the short arms (p11) of the acrocentric chromosomes and other heterochromatic regions. This DNA sequence analysis suggested that the terminal deficiency in this 18q-syndrome patient arose via illegitimate (non-homologous) recombination. Moreover, these data raise the possibility that a subset of chromosomal aberrations appearing cytogenetically and molecularly as simple terminal truncations or deletions are caused by small (<1000 kb) cryptic rearrangements.

FISH analysis of terminal deletions in patients diagnosed with cri-du-chat syndrome.

Most patients with cri-du-chat syndrome have a de novo deletion of the short arm of chromosome 5 (5p). In order to perform extensive phenotype-genotype correlation studies, a relatively easy method for the precise determination of the extent of a patient's deletion is essential. Towards this purpose, a set of minimally overlapping YAC clones that span 5p was identified. A BAC that maps at or near the 5p telomere was also used. A total of 110 patients with previously determined de novo terminal deletions by standard cytogenetic approaches were reanalyzed using the YAC clones and fluorescent in situ hybridization (FISH). Of the 110 samples, 4 patients were determined to have interstitial deletions, 1 patient had an unbalanced translocation, and no deletion could be detected in 2 patients. The FISH results in the 7 patients affect the clinical prognosis for some of these patients. These results demonstrate the need for supplementing standard cytogenetics with FISH analysis when an abnormal karyotype is detected.

t(1;18)(q32.1;q22.1) associated with genitourinary malformations.

We report a male infant who has impaired penile development, hypospadias, and mild developmental delay with a 46,XY,t(1;18)(q32.1;q22.1) karyotype. Fluorescent in situ hybridization (FISH) was performed to more precisely map the translocation breakpoint. The translocation breakpoint maps to a region that has been implicated in genitourinary malformations in the 18q- syndrome. This case report suggests that a gene involved in genitourinary development maps at or near the chromosome 18 translocation breakpoint.

Refined chromosomal localization of the mismatch repair and hereditary nonpolyposis colorectal cancer genes hMSH2 and hMSH6.

The genomic loci for the mismatch repair genes hMSH2 and hMSH6 were mapped by fluorescence in situ hybridization, analysis of radiation hybrid panel markers, and linkage analysis of syntenic chromosome regions between human and mouse. Both genes were localized to chromosome 2p21, adjacent to the luteinizing hormone/choriogonadotropin receptor gene (LHCGR; 2p21), telomeric to the D2S123 polymorphic marker, and centromeric to the calmodulin-2 gene (CALM-2; 2p22-21) and son-of-sevenless gene (SOS; 2p22-21). The genomic locations of hMSH2 and hMSH6 appears to be within 1 Mb of each other because they could not be separated by interphase fluorescence in situ hybridization. These results clarify the position of the chromosome 2 hereditary nonpolyposis colorectal cancer locus, which was originally reported to be associated with an adjacent region (chromosome 2p14-16).

Human exonuclease I interacts with the mismatch repair protein hMSH2.

DNA mismatch repair (MMR) plays a vital role in the faithful replication of DNA, and its inactivation leads to a mutator phenotype that has been associated with the common cancer susceptibility syndrome Hereditary Non-Polyposis Colorectal Cancer (HNPCC). Here, we report on a novel human exonuclease (hExoI) that is related to the yeast exonuclease 1. The hExoI cDNA comprises 2541 bp, which code for a Mr 94,000 protein that appears to be highly expressed in testis tissue and at very low levels in other tissues. The hExoI gene has 14 exons and is located on chromosome 1q43, as determined by fluorescence in situ hybridization and radiation hybrid mapping. hExoI was found to interact strongly with the human MMR protein hMSH2, suggesting its involvement in the MMR process and/or DNA recombination.

Affective disorder associated with a balanced translocation involving chromosome 14 and 18.

We report a case of a women with psychiatric illness that includes bipolar disorder who has a karyotype of 46,XX,t(14;18)(q11.2;q22.1). The region on chromosome 18 that is involved in the translocation has been implicated in other families through linkage and association studies as possibly containing a gene for bipolar illness.