Genealogical analysis of cystic fibrosis families and chromosome 7q RFLP haplotypes in the Hutterite Brethren.

In the 100-year period 1880-1980 the Hutterite population increased from about 442 to 23,000 individuals in North America. There are three endogamous subdivisions in this Caucasian genetic isolate. A total of 11 cystic fibrosis (CF) families from Canada and the United States were investigated, including at least two families from each of the three subdivisions, the Dariusleut, Lehrerleut, and Schmiedeleut. A study of RFLPs for the loci D7S8, D7S23, MET, and D7S18 (also called D7S16) in the region of the CF gene in 10 families shows considerable genetic variability. There were three different extended CF gene-region haplotypes on CF chromosomes (CF haplotypes), and there were 13 different extended CF gene-region haplotypes on normal chromosomes (normal haplotypes). The three CF haplotypes have different D7S23 and MET haplotypes. Parents who have the same CF haplotype are, on the average, more closely related than parents who have different haplotypes, but only within the same subdivision. A marriage node graph of 11 families illustrates the complexity of Hutterite genealogies. The frequency distribution of CF haplotypes in the Hutterite sample differs notably from those of larger agglomerates of family data from collaborative studies, with respect to D7S8, MET haplotypes, and D7S23 haplotypes. We propose that there were at least three CF carriers among the founders of the Hutterite population and that copies of a particular CF haplotype in current individuals are identical by descent. The alternative that one or more genetically distinguishable CF haplotypes resulted from recombination since the founding of the population is considered to be less likely.     

Refined linkage map of chromosome 7 in the region of the cystic fibrosis gene

The genetic map in the region of human chromosome 7 that harbors the gene for cystic fibrosis (CF) has been refined by multilocus linkage studies in an expanded database including a large set of normal families. Six loci known to be linked to CF were examined: MET, an oncogene; COL1A2, collagen; TCRB, T-cell-receptor beta polypeptide; and three arbitrary loci—D7S8, D7S13, and D7S16—defined by probes pJ3.11, pB79a, and p7C22, respectively. The gene order with greatest statistical support is COL1A2-D7S13-D7S16-MET-D7S8-TCRB. Linkage analysis in families segregating for CF suggested that the most likely location of the CF gene on this map is between MET and D7S8.     

Identification and regional localization of DNA markers on chromosome 7 for the cloning of the cystic fibrosis gene

To facilitate mapping of the cystic fibrosis locus (CF) and to isolate the corresponding gene, we have screened a flow-sorted chromosome 7-specific library for additional DNA markers in the 7q31-q32 region. Unique ("single-copy") DNA segments were selected from the library and used in hybridization analysis with a panel of somatic cell hybrids containing various portions of human chromosome 7 and patient cell lines with deletion of this chromosome. A total of 258 chromosome 7-specific single-copy DNA segments were identified, and most of them localized to subregions. Fifty three of these corresponded to DNA sequences in the 7q31-q32 region. Family and physical mapping studies showed that two of the DNA markers, D7S122 and D7S340, are in close linkage with CF. The data also showed that D7S122 and D7S340 map between MET and D7S8, the two genetic markers known to be on opposite sides of CF. The study thus reaffirms the general strategy in approaching a disease locus on the basis of chromosome location.     

Localization of the gene for plasma retinol binding protein to the distal half of mouse chromosome 19

A DNA polymorphism for the mouse retinol binding protein has been identified using the enzyme BamHI and a rat partial cDNA probe. Analysis of the polymorphism in DNA from 64 inbred mouse strains demonstrated the presence of a single gene with two alleles, Rbp-4b and Rbp-4d. Comparison of the segregation patterns of these alleles in three sets of recombinant inbred strains with allele segregation patterns of previously characterized loci shows that the Rbp-4 locus is closely linked to the locus for phenobarbital-inducible cytochrome P450-2c (Cyp-2c) that has been shown by in situ hybridization to lie on chromosome 19, bands D1-D2. The Rbp-4 locus is just proximal to Cyp-2c at the distal end of chromosome 19.     

Owl monkey gene map: evidence for a homologous human chromosome 7q region near the cystic fibrosis locus

We have demonstrated the assignments of two gene loci (COLIA2, MET) and two noncoding DNA markers (D7S13, D7S8) to owl monkey chromosome 14 (K-VI) by hybridizing DNA probes from the cystic fibrosis (CF) region of human chromosome 7q21-32 to panels of rodent-owl monkey somatic cell hybrids. The assignments are substantiated by in situ chromosome hybridization of markers COLIA2, MET, and D7S13 to the distal long arm of chromosome 14 (K-VI). These results support genomic conservation of the human CF region, at least in the higher primates.     

RFLP haplotyping and mutation analysis of the phenylalanine hydroxylase gene in Dutch phenylketonuria families

Restriction fragment length polymorphism haplotyping of mutated and normal phenylalanine hydroxylase (PAH) alleles in 49 Dutch phenylketonuria (PKU) families was performed. All mutant PAH chromosomes identified by haplotyping (n = 98) were screened for eight of the most predominant mutations. Compound heterozygosity was proven in 40 kindreds. Homozygosity was found for the IVS12nt1 mutation in 5 families, and for the R158Q and IVS10nt546 mutations in one family each. All patients from these families suffer from severe PKU, providing additional proof that these mutations are deleterious for the PAH gene. Genotypical heterogeneity was evident for mutant haplotype 1 (n = 27) carrying the mutations R261Q (n = 12), E280K (n = 4), P281L (n = 1) and unknown (n = 10), and likewise for mutant haplotype 4 (n = 30) carrying the mutations R158Q (n = 13), Y414C (n = 1) and unknown (n = 16). Mutant haplotype 3 (n = 20), in tight association with mutation IVS12nt1, appeared to be in strong linkage disequilibrium (LDE) with its normal counterpart allele (n = 4). Mutant haplotype 6 (n = 4), in tight association with the IVS10nt546 mutation, showed moderate LDE with its counterpart allele (n = I). The distribution of the mutant PAH haplotypes 1, 3 and 4 among the Dutch PKU population resembles that in other Northern and Western European countries, but it is striking that mutant haplotype 2 and its associated mutation R408W is nearly absent in The Netherlands, in strong contrast to its neighbouring countries.     

The Kell blood group locus is close to the cystic fibrosis locus on chromosome 7

Summary Linkage analysis confirmed the assignment of the Kell blood group locus to chromosome 7.     

Analysis of the complete coding region of the CFTR gene in ten Algerian cystic fibrosis families

The spectrum of cystic fibrosis (CF) mutations in the North African population remains poorly known. In order to offer an effective diagnostic service and to determine accurate risk estimates, we decided to identify the CF mutations in 10 Algerian CF families. We carried out a chemical-clamp denaturing gradient gel electrophoresis analysis of the CFTR gene and automated direct DNA sequencing. We identified 5 mutations and we characterized 60% of the CF chromosomes. Taking advantage of the homogeneity of the sample, we report clinical features of homozygous CF patients.     

Localization of the gene for human heart fatty acid binding protein to chromosome 1p32-1p33

Among 639 spontaneous abortions between the 8th and 14th week of gestation 342 (53.5%) revealed an abnormal karyotype. While the rate of trisomies distinctly increased with advancing maternal age, a decrease in the rate of 45,X conceptuses and polyploidies was observed among abortions from older women. The overall relation of XXXXXXYY among the tetraploidies was 1411 and that of XXXXXYXYY among the triploidies was 26 361. However, when the latter was related to maternal age, a reversal of the XXXXXY ratio of 12 in the younger to 21 in the older age groups became evident. Furthermore a decrease in the rate of paternally derived partial hydatidiform moles was found among the triploid abortion specimens from older women. From these observations we conclude that digyny plays a major role in the origin of triploidy in the increased maternal age groups, while diandry related to immaturity of oocytes and impairment of oocyte cortical function is more frequent in triploid abortions from younger women.     

A mutation in the second nucleotide binding fold of the cystic fibrosis gene.

The discovery last year of the deletion of a phenylalanine residue at amino acid position 508 of the cystic fibrosis (CF) gene has meant that approximately 70% of mutant chromosomes associated with CF can be accounted for. We report the finding of a substitution at nucleotide position 4041 of the CF gene, resulting in a change from asparagine to lysine at amino acid position 1303. We believe that this is a disease-causing mutation, as it involves a nonconservative amino acid change and has only been found on CF chromosomes with a consistent haplotype background. The mutation was detected using direct sequencing of PCR-amplified genomic DNA and was confirmed by dot hybridization to both normal and mutant allele-specific oligonucleotides. The mutation was detected on three chromosomes from four individuals but not on any normal chromosome. Its presence in the heterozygous state is not correlated with the clinical status of the individual patients.     

The gene for the alpha i1 subunit of human guanine nucleotide binding protein maps near the cystic fibrosis locus.

The gene for the alpha i1 subunit of human guanine nucleotide binding (G) protein was mapped by in situ hybridization to chromosome 7 at band q21. The regional chromosomal location of the human alpha i1 gene was confirmed using human/mouse somatic-cell hybrid lines containing portions of human chromosome 7. Because the alpha i1 gene mapped near the cystic fibrosis locus and because an abnormal G protein might be expected to contribute to the pathophysiology of this disease, the alpha i1 gene was mapped with respect to the cystic fibrosis locus as defined by the Met oncogene and anonymous DNA marker pJ3.11. The location of the alpha i1 gene proved to be distinct from that of the cystic fibrosis locus.     

The human chromogranin A gene: chromosome assignment and RFLP analysis.

Chromogranin A/secretory protein I (CgA) is a glycoprotein that is stored and released along with peptide hormones and neurotransmitters from several tissues, although its exact function is not known. A cDNA (gene symbol CHGA) clone was used as a probe in Southern blot analyses of human-rodent somatic cell hybrid DNAs. Discordancy analysis allowed confirmation of the assignment of the gene to chromosome 14. These results were extended using in situ chromosome hybridization, and a signal was found at 14q32. BglII digestion of genomic DNA from 28 unrelated Caucasian individuals probed with CHGA detected a two-allele RFLP with allelic frequencies of .34 and .66.