Additional mutations in the cystic fibrosis (CF) gene were identified in the regions corresponding to the two putative nucleotide (ATP)-binding folds (NBFs) of the predicted polypeptide. The patient cohort included 46 Canadian CF families with well-characterized DNA marker haplotypes spanning the disease locus and several other families from Israel. Eleven mutations were found in the first NBF, 2 were found in the second NBF, but none was found in the R-domain. Seven of the mutations were of the missense type affecting some of the highly conserved amino acid residues in the first NBF; 3 were nonsense mutations; 2 would probably affect mRNA splicing; 2 corresponded to small deletions, including another 3-base-pair deletion different from the major mutation (AF508), which could account for 70% of the CF chromosomes in the population. Nine of these mutations accounted for 12 of the 31 non-AF508 CF chromosomes in the Canadian families. The highly heterogeneous nature of the remaining CF mutations provides important insights into the structure and function of the protein, but it also suggests that DNA-based genetic screening for CF carrier status will not be straightforward.

Clozapine is a particularly effective antipsychotic medication but its use is curtailed by the risk of clozapine-induced agranulocytosis/granulocytopenia (CIAG), a severe adverse drug reaction occurring in up to 1% of treated individuals. Identifying genetic risk factors for CIAG could enable safer and more widespread use of clozapine. Here we perform the largest and most comprehensive genetic study of CIAG to date by interrogating 163 cases using genome-wide genotyping and whole-exome sequencing. We find that two loci in the major histocompatibility complex are independently associated with CIAG: a single amino acid in HLA-DQB1 (126Q) (P=4.7×10−14, odds ratio, OR=0.19, 95% CI 0.12–0.29) and an amino acid change in the extracellular binding pocket of HLA-B (158T) (P=6.4×10−10, OR=3.3, 95% CI 2.3–4.9). These associations dovetail with the roles of these genes in immunogenetic phenotypes and adverse drug responses for other medications, and provide insight into the pathophysiology of CIAG.

The use of polymerase chain reaction (PCR) and oligonucleotide hybridization offers a new approach for the definition of HLA class II alleles. It has been possible to determine 43 alleles of DRB1, four of DRB3, two of DRB4, four of DRB5, eight of DQA1, and 14 of DQB1. These alleles are inherited together in members of families and form closely associated groups which are found repeatedly and in characteristic patterns in different populations. We have determined the HLA class II alleles and analyzed their association in 431 healthy unrelated subjects including 161 North American Caucasians, 53 Latin Americans, 61 Blacks, 88 Chinese, and 68 Israeli Jews. For-locus haplotypes (DRB1; DRB3/4/5; DQA1; DQB1) were derived from 79 B cell lines and the analysis of segregation in 34 nuclear families. The B-cell lines yielded 37 and the families showed the same, and 20 other, haplotypic combinations. In addition to these 57 haplotypes, associated alleles were assigned in the unrelated panels following certain rules. The resulting haplotypes were assigned to groups known to share associated alleles. The groups were: 1) DR1, DR2, and DRw10 (13 haplotypes); 2) DR3 and DRw6 (26 haplotypes); 3) DR5 and DRw8 (24 haplotypes); 4) DR4, DR7, and DR9 (24 haplotypes). Their distribution in populations with different ethnic backgrounds was analyzed. The expressed DRB4 allele and its null mutant were determined by PCR and oligonucleotide hybridization. The different DR7 haplotypes resulting from these determinations were analyzed in a panel of 130 North American Caucasoids. This comprehensive analysis of class II HLA haplotypes in human populations should be useful in understanding the role of these genes and in various applications including anthropology, disease susceptibility, and transplantation of allogeneic organs and tissues.