Genetic restriction of AIDS pathogenesis by an SDF-1 chemokine gene variant. ALIVE Study, Hemophilia Growth and Development Study (HGDS), Multicenter AIDS Cohort Study (MACS), Multicenter Hemophilia Cohort Study (MHCS), San Francisco City Cohort (SFCC)

Stromal-derived factor (SDF-1) is the principal ligand for CXCR4, a coreceptor with CD4 for T lymphocyte cell line-tropic human immunodeficiency virus-type 1 (HIV-1). A common polymorphism, SDF1-3'A, was identified in an evolutionarily conserved segment of the 3' untranslated region of the SDF-1 structural gene transcript. In the homozygous state, SDF1-3'A/3'A delays the onset of acquired immunodeficiency syndrome (AIDS), according to a genetic association analysis of 2857 patients enrolled in five AIDS cohort studies. The recessive protective effect of SDF1-3'A was increasingly pronounced in individuals infected with HIV-1 for longer periods, was twice as strong as the dominant genetic restriction of AIDS conferred by CCR5 and CCR2 chemokine receptor variants in these populations, and was complementary with these mutations in delaying the onset of AIDS.

Novel alleles of the chemokine-receptor gene CCR5

The CCR5 gene encodes a cell-surface chemokine-receptor molecule that serves as a coreceptor for macrophage-tropic strains of HIV-1. Mutations in this gene may alter expression or function of the protein product, thereby altering chemokine binding/signaling or HIV-1 infection of cells that normally express CCR5 protein. Indeed, homozygotes for a 32-bp deletion allele of CCR5 (CCR5-delta 32), which causes a frameshift at amino acid 185, are relatively resistant to HIV-1 infection. Here we report the identification of 16 additional mutations in the coding region of the CCR5 gene, all but 3 of which are codon altering or "nonsynonymous." Most mutations were rare (found only once or twice in the sample); five were detected exclusively among African Americans, whereas eight were observed only in Caucasians. The mutations included 11 codon-altering nonsynonymous variants, one trinucleotide deletion, one chain-termination mutant, and three synonymous mutations. The high predominance of codon-altering alleles among CCR5 mutants (14/17 [81%], including CCR5-delta 32) is consistent with an adaptive accumulation of function-altering alleles for this gene, perhaps as a consequence of historic selective pressures.

[Population features of gene mutation frequency of the CKR-5 receptor, determining sensitivity to the AIDS virus]

Recently, it was shown that a 32-bp deletion in the CKR5 macrophage chemokine receptor gene produced resistance to HIV infection. Frequencies of the CKR5 mutant allele in Russians, Tatars, Uzbeks, Kazakhs, Azerbaijanis, Uigurts, Tuvinians, and Georgians estimated by means of the PCR technique were equal to 0.13, 0.12, 0.85, 0.06, 0.05, 0.04, 0.03, and 0.00, respectively. While the theoretically expected frequency of deletion homozygotes in Russians and Tatars was 1.7%, none of such homozygotes were detected among the 90 persons examined. The data suggested that about 25% of the population in northwestern Russia is highly resistant to HIV infection.

Identification of a fourth half ABC transporter in the human peroxisomal membrane

Three half ATP-binding cassette transporters (ALDP, ALDR, PMP70) are known to be present in the human peroxisome membrane. Mutations in the gene encoding ALDP cause X-linked adrenoleukodystrophy; the role of ALDR and PMP70 in human disease is unclear. We report the cloning and characterization of a fourth human gene encoding a peroxisomal half ABC transporter. The gene, designated P70R, maps to chromosome 14q24, encodes a 73 kDa transporter most similar to PMP70, and is expressed in all human tissues examined. Because half ABC transporters heterodimerize to form functional transporters, the identification of a fourth member of this family in the peroxisome membrane has implications for our understanding of mammalian peroxisomes and the genetic disorders of peroxisomal function.

Mutation of the Stargardt disease gene (ABCR) in age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of severe central visual impairment among the elderly and is associated both with environmental factors such as smoking and with genetic factors. Here, 167 unrelated AMD patients were screened for alterations in ABCR, a gene that encodes a retinal rod photoreceptor protein and is defective in Stargardt disease, a common hereditary form of macular dystrophy. Thirteen different AMD-associated alterations, both deletions and amino acid substitutions, were found in one allele of ABCR in 26 patients (16%). Identification of ABCR alterations will permit presymptomatic testing of high-risk individuals and may lead to earlier diagnosis of AMD and to new strategies for prevention and therapy.

Contrasting genetic influence of CCR2 and CCR5 variants on HIV-1 infection and disease progression. Hemophilia Growth and Development Study (HGDS), Multicenter AIDS Cohort Study (MACS), Multicenter Hemophilia Cohort Study (MHCS), San Francisco City Cohort (SFCC), ALIVE Study

The critical role of chemokine receptors (CCR5 and CXCR4) in human immunodeficiency virus-type 1 (HIV-1) infection and pathogenesis prompted a search for polymorphisms in other chemokine receptor genes that mediate HIV-1 disease progression. A mutation (CCR2-64I) within the first transmembrane region of the CCR2 chemokine and HIV-1 receptor gene is described that occurred at an allele frequency of 10 to 15 percent among Caucasians and African Americans. Genetic association analysis of five acquired immunodeficiency syndrome (AIDS) cohorts (3003 patients) revealed that although CCR2-64I exerts no influence on the incidence of HIV-1 infection, HIV-1-infected individuals carrying the CCR2-64I allele progressed to AIDS 2 to 4 years later than individuals homozygous for the common allele. Because CCR2-64I occurs invariably on a CCR5-+-bearing chromosomal haplotype, the independent effects of CCR5-Delta32 (which also delays AIDS onset) and CCR2-64I were determined. An estimated 38 to 45 percent of AIDS patients whose disease progresses rapidly (less than 3 years until onset of AIDS symptoms after HIV-1 exposure) can be attributed to their CCR2-+/+ or CCR5-+/+ genotype, whereas the survival of 28 to 29 percent of long-term survivors, who avoid AIDS for 16 years or more, can be explained by a mutant genotype for CCR2 or CCR5.

Auditory and tactile bone-conduction thresholds using three different oscillators

Determination of tactile bone-conduction (BC) thresholds is essential to provide proper diagnosis of individuals with profound hearing loss. In this study, auditory and tactile BC thresholds were compared using three oscillators: the Radioear B-70-A, B-71, and B-72 with mastoid and forehead placement. Subjects included 12 adults with normal hearing (to establish auditory thresholds) and 12 adults with profound sensorineural hearing loss (to establish tactile thresholds). All 24 subjects were tested at octave intervals from 250 through 4000 Hz. As demonstrated in previous studies, tactile thresholds were lower for the low frequencies. Some differences in tactile thresholds were evinced as a function of different oscillators. One fact that emerged from this study is the lower tactile threshold with forehead placement as compared to the mastoid. While ostensibly a disadvantage to forehead BC testing, there are some clinical advantages to be gleaned from this discovery.

Germline and somatic mutations in the tyrosine kinase domain of the MET proto-oncogene in papillary renal carcinomas

Hereditary papillary renal carcinoma (HPRC) is a recently recognized form of inherited kidney cancer characterized by a predisposition to develop multiple, bilateral papillary renal tumours. The pattern of inheritance of HPRC is consistent with autosomal dominant transmission with reduced penetrance. HPRC is histologically and genetically distinct from two other causes of inherited renal carcinoma, von Hippel-Lindau disease (VHL) and the chromosome translocation (3;8). Malignant papillary renal carcinomas are characterized by trisomy of chromosomes 7, 16 and 17, and in men, by loss of the Y chromosome. Inherited and sporadic clear cell renal carcinomas are characterized by inactivation of both copies of the VHL gene by mutation, and/or by hypermethylation. We found that the HPRC gene was located at chromosome 7q31.1-34 in a 27-centimorgan (cM) interval between D7S496 and D7S1837. We identified missense mutations located in the tyrosine kinase domain of the MET gene in the germline of affected members of HPRC families and in a subset of sporadic papillary renal carcinomas. Three mutations in the MET gene are located in codons that are homologous to those in c-kit and RET, proto-oncogenes that are targets of naturally-occurring mutations. The results suggest that missense mutations located in the MET proto-oncogene lead to constitutive activation of the MET protein and papillary renal carcinomas.

Isolation and chromosomal mapping of a novel ATP-binding cassette transporter conserved in mouse and human

We report here on the identification and genomic mapping of a novel member of the family of the ATP-binding cassette (ABC) transporters, ABC7, conserved in mouse and in humans. The ABC7 gene encodes a protein with the typical features of half-transporters, such as those involved in translocation of antigenic peptides or in peroxisomal disorders. ABC7 shows a ubiquitous expression pattern and maps to the X chromosome both in mouse and in humans. The high sequence similarity to those of two yeast half-transporters supports once again the extreme evolutionary conservation of this family of proteins.

Benign prostatic hyperplasia

Benign prostatic hyperplasia is a common problem in men over 50, causing unpleasant symptoms. This Update examines the range of treatments now available, including traditional interventions and modern techniques.

A photoreceptor cell-specific ATP-binding transporter gene (ABCR) is mutated in recessive Stargardt macular dystrophy

Stargardt disease (STGD, also known as fundus flavimaculatus; FFM) is an autosomal recessive retinal disorder characterized by a juvenile-onset macular dystrophy, alterations of the peripheral retina, and subretinal deposition of lipofuscin-like material. A gene encoding an ATP-binding cassette (ABC) transporter was mapped to the 2-cM (centiMorgan) interval at 1p13-p21 previously shown by linkage analysis to harbour the STGD gene. This gene, ABCR, is expressed exclusively and at high levels in the retina, in rod but not cone photoreceptors, as detected by in situ hybridization. Mutational analysis of ABCR in STGD families revealed a total of 19 different mutations including homozygous mutations in two families with consanguineous parentage. These data indicate that ABCR is the causal gene of STGD/FFM.

Characterization of a YAC contig containing the NBCCS locus and a novel Kruppel-type zinc finger sequence on chromosome segment 9q22.3

Gorlin's syndrome or nevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant disorder characterized by a familial or hereditary predisposition to basal cell carcinomas (generally multiple and of early onset), odontogenic keratocysts (jaw cysts), palmar and plantar pits, a wide variety of developmental defects, as well as cancers such as medulloblastomas and ovarian fibromas. The gene for NBCCS has been mapped to human chromosome region 9q22.1-q31 by linkage analysis and by cytogenetic evidence of deletions in this region in patients with the syndrome. This is supported by loss of heterozygosity in tumors of polymorphic marker loci flanked by D9S197 and D9S180. We have utilized sequence tagged site (STS) mapping and somatic cell hybrid panel analysis to construct two overlapping yeast artificial chromosome (YAC) contigs spanning this region of the genome. We used the YAC contigs to identify a new zinc finger gene containing a highly informative microsatellite locus.

Pulsed-field gel electrophoresis and FISH mapping of chromosome 9q22: placement of a novel zinc finger gene within the NBCCS and ESS1 region

Chromosome 9q22 is a gene-rich region to which several human disease loci have been mapped. Pulsed field gel electrophoresis (PFGE) and FISH were used to determine the order of and distance between 12 chromosome 9q22 markers flanked by D9S196 and D9S180. D9S780 and XPA were within 190 kb of each other and hybridized to the same 460-kb NotI fragment as D9S180. ZNF169, a novel kruppel-type gene, and D9S280 shared several PFGE fragments indicating that they are not more than 300 kb apart. Interphase FISH showed that COL15A1 lies distal to the region bounded by D9S180 and D9S196 and that ZNF169 is adjacent to D9S196. Based on the restriction fragment lengths in this region and estimates from FISH, the distance from D9S180 to D9S196 is not less than 2 Mb.