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Nonsyndromic hearing impairment is one of the most heterogeneous hereditary conditions, with more than 40 loci mapped on the human genome, however, only a limited number of genes implicated in hearing loss have been identified. We previously reported linkage to chromosome 7p15 for autosomal dominant hearing impairment segregating in an extended Dutch family (DFNA5). Here, we report a further refinement of the DFNA5 candidate region and the isolation of a gene from this region that is expressed in the cochlea. In intron 7 of this gene, we identified an insertion/deletion mutation that does not affect intron-exon boundaries, but deletes five G-triplets at the 3' end of the intron. The mutation co-segregated with deafness in the family and causes skipping of exon 8, resulting in premature termination of the open reading frame. As no physiological function could be assigned, the gene was designated DFNA5.

The tectorial membrane is an extracellular matrix of the inner ear that contacts the stereocilia bundles of specialized sensory hair cells. Sound induces movement of these hair cells relative to the tectorial membrane, deflects the stereocilia, and leads to fluctuations in hair-cell membrane potential, transducing sound into electrical signals. Alpha-tectorin is one of the major non-collagenous components of the tectorial membrane. Recently, the gene encoding mouse alpha-tectorin (Tecta) was mapped to a region of mouse chromosome 9, which shows evolutionary conservation with human chromosome 11q (ref. 3), where linkage was found in two families, one Belgian (DFNA12; ref. 4) and the other, Austrian (DFNA8; unpublished data), with autosomal dominant non-syndromic hearing impairment. We determined the complete sequence and the intron-exon structure of the human TECTA gene. In both families, mutation analysis revealed missense mutations which replace conserved amino-acid residues within the zona pellucida domain of TECTA. These findings indicate that mutations in TECTA are responsible for hearing impairment in these families, and implicate a new type of protein in the pathogenesis of hearing impairment.

A gene for an autosomal dominant form of progressive sensorineural hearing loss (DFNA5) was previously assigned by us to a 15-cM region on chromosome 7p15. In this study, the DFNA5 candidate region was refined to less than 2 cM, and completely cloned in a YAC contig. The HOXA1 gene located in 7p15 was considered to be a good candidate gene for DFNA5 as it harbours mutations leading to developmental defects of the inner ear in mice. However, the refinement of the candidate region of DFNA5 excludes the HOXA1 gene as a candidate for DFNA5. We cloned a novel candidate gene (CG1, candidate gene 1), which is expressed in human fetal cochlea, from the DFNA5 candidate region. The complete cDNA sequence of CG1, encoding a 423 amino acid protein of unknown function, was determined. Mutation analysis of the CG1 gene in DFNA5 patients, however, could not reveal a disease-causing mutation.

Nonsyndromic hearing loss (NSHL) is the most common type of hearing impairment in the elderly. Environmental and hereditary factors play an etiologic role, although the relative contribution of each is unknown. To date, 39 NSHL genes have been localized. Twelve produce autosomal dominant hearing loss, most frequently postlingual in onset and progressive in nature. We have ascertained a large, multigenerational family in which a gene for autosomal dominant NSHL is segregating. Affected individuals experience progressive hearing loss beginning in the 2d-4th decades, eventually making the use of amplification mandatory. A novel locus, DFNA13, was identified on chromosome 6p; the disease gene maps to a 4-cM interval flanked by D6S1663 and D6S1691, with a maximum two-point LOD score of 6.409 at D6S299.

A cluster of homeobox-containing genes (HOXA) and a heterogeneous nuclear ribonucleoprotein (hnRPA2B1) have both previously been assigned to chromosome 7p15 by in situ hybridization. In this report, we constructed a YAC contig from chromosome 7p14-p15, between markers D7S2496 and D7S1838, and determined the position of the HOXA1 gene and the hnRPA2B1 gene in this YAC contig.

We performed linkage analysis in a Belgian family with autosomal dominant midfrequency hearing loss, which has a prelingual onset and a nonprogressive course in most patients. We found LOD scores >6 with markers on chromosome 11q. Analysis of key recombinants maps this deafness gene (DFNA12) to a 36-cM interval on chromosome 11q22-24, between markers D11S4120 and D11S912. The critical regions for the recessive deafness locus DFNB2 and the dominant locus DFNA11, which were previously localized to the long arm of chromosome 11, do not overlap with the candidate interval of DFNA12.

Late-onset non-syndromic hearing impairment is the most common type of neurological dysfunction in the elderly. It can be either acquired or inherited, although the relative impact of heredity on this type of loss is not known. To date, nine different genes have been localized, but none has been cloned. Using an extended American family in which a gene for autosomal dominant late-onset non-syndromic hearing impairment is segregating, we have identified a new locus, DFNA10, on chromosome 6.

Progressive hearing loss affects approximately 50% of the elderly by the age of 80, and is most likely caused by an interaction of genetic and environmental factors. Identification of the genes responsible for hereditary hearing loss is therefore important. Families with pure genetic degenerative hearing disorders may be helpful as the same genes may be also involved in age-related hearing loss in general. In this study we have performed a genome search in an extended Dutch family with autosomal dominant progressive hearing loss starting in the high frequencies. The gene causing hearing loss in this family was localized to the short arm of chromosome 7, in a 15 cM interval between markers D7S493 and D7S632.

The cellular immune responses to fractionated Haemophilus ducreyi antigens, coated on latex beads, were assessed in patients with chancroid and in controls, using an in vitro lymphocyte proliferation assay. Several fractions of H. ducreyi antigen revealed stimulating activity. However, only the molecular size ranges 91-78 kD, 59-29 kD, and 25-21 kD induced proliferation that may be specifically related to H. ducreyi infection. Lymphocytes from four HIV- patients, successfully treated for chancroid, were not stimulated by H. ducreyi antigen. In general, lymphocytes from HIV+ chancroid patients were less responsive to H. ducreyi antigen compared with those from HIV- chancroid patients. However, two HIV-infected patients showed exceptionally strong responses to high molecular weight fractions. To our knowledge this is the first report demonstrating that H. ducreyi contains specific T cell-stimulating antigens. Based on this work, further identification and purification of the T cell antigens is feasible.

Calmodulin-binding proteins in chromaffin granule membrane and chromaffin cell plasma membranes have been investigated and compared. Chromaffin granules were purified by centrifugation over a 1.7 M sucrose layer. Plasma membranes were obtained in a highly purified form by differential and isopycnic centrifugation. Enzymatic determinations of 5'-nucleotidase, a generally accepted plasma membrane marker, showed a 40-50-fold enrichment as compared to the cell homogenate. Marker enzyme studies demonstrated only minimal contamination by other subcellular organelles. After solubilization with Triton X-100, calmodulin-binding proteins were isolated from chromaffin granule membranes and plasma membranes by affinity chromatography on a calmodulin/Sepharose 4B column. On two-dimensional polyacrylamide gelelectrophoresis a prominent protein (Mr = 65,000, pI ranging from 5.1 to 6) consisting of multiple spots, was present in the calmodulin-binding fraction from chromaffin granule membranes as well as from plasma membranes. Besides this 65 kDa protein both fractions had at least four groups of proteins in common. Also, proteins typical for either preparation were observed. In the calmodulin-binding protein preparations from chromaffin granule membranes a prominent spot with Mr = 80,000 and a pH ranging from 5.0 to 5.7 was present. This protein was enzymatically and immunologically identified as dopamine-beta-monooxygenase.

The procedures used in the investigation of low back pain and sciatica have been subjected to a double statistical analysis to determine their diagnostic accuracy, since contradictory opinions have been expressed in the literature. It was found that only lumbar phlebography was more accurate than the most simple procedure, the clinical examination. Myelography is more accurate than clinical examination only in making a positive diagnosis. In this case, it equals the reliability of lumbar phlebography, but so does plain film radiography which however leads to a positive diagnosis less constantly. Lumbar phlebography is the most accurate procedure for making a negative diagnosis, mainly by avoiding a false negative conclusion. A comparison is made with the statements in the literature and the complementary use of the different procedures is proposed for the investigation of low back pain and sciatica.