A missense mutation in the LIM2 gene is associated with autosomal recessive presenile cataract in an inbred Iraqi Jewish family

In an inbred Iraqi Jewish family, we have studied three siblings with presenile cataract first noticed between the ages of 20 and 51 years and segregating in an autosomal recessive mode. Using microsatellite repeat markers in close proximity to 25 genes and loci previously associated with congenital cataracts in humans and mice, we identified five markers on chromosome 19q that cosegregated with the disease. Sequencing of LIM2, one of two candidate genes in this region, revealed a homozygous T-->G change resulting in a phenylalanine-to-valine substitution at position 105 of the protein. To our knowledge, this constitutes the first report, in humans, of cataract formation associated with a mutation in LIM2. Studies of late-onset single-gene cataracts may provide insight into the pathogenesis of the more common age-related cataracts.     

Mapping of new recessive cataract gene (itIr2) in the mouse

A new strain of mice with cataracts was developed in BALB/cHeA and STS/A recombinant inbred strain, CXS4 (D). In this study the mapping of spontaneous autosomal recessive cataract mutation is described. This mutation was characterized by ruptures of the lens nucleus, vitreous chamber through the posterior capsule, and the vacuolization of the lens. For the linkage analysis, we produced two kinds of backcross progenies, (BALB/cHeA × D)F₁ and (STS/A × D)F₁ females crossed to D male mice. The gene (lr2, lens rupture2) was mapped to the central part of Chromosome(Chr) 14, 0.7 ± 0.7cM from the micosatellite marker D14Mit28. Received: 13 October 1996 / Accepted: 22 July 1997     

Hereditary hepatitis of LEC rats is controlled by a single autosomal recessive gene

The natural history of hereditary hepatitis in long-survived LEC rats was reported. Among 56 (female: male, 28:28) LEC rats of F30, 16 (8:8) (29%) died of fulminant hepatitis approximately four months after birth. The remaining 40 (20:20) rats that survived more than one year developed chronic hepatitis and subsequent hepatic lesions including hepatocellular carcinomas. Further study made with 32 F31 rats killed at the age of five months revealed that hepatitis occurred in all of these rats. Genetic analysis performed by various crosses of LEC and LEJ rats confirmed the previous result that hereditary hepatitis was caused by a single autosomal recessive gene. F1 hybrid rats never developed hepatitis, showing normal histology of the liver. Histological features of hepatitis in F2 (F1 X F1) and backcross (F1 X LEC) rats were the same as those observed in the LEC rats. The preneoplastic foci also appeared in some of these hybrid rats at the age of eight months. We propose a gene symbol hts to designate the present hepatitis which is assumed to be homozygous in LEC strain rats.     

Deamidation in human gamma S-crystallin from cataractous lenses is influenced by surface exposure

A major component of human nuclear cataracts is water-insoluble, high molecular weight protein. A significant component of this protein is disulfide bonded gamma S-crystallin that can be reduced to monomers by dithiothreitol. Analysis of this reduced gamma S-crystallin showed that deamidation of glutamine and asparagine residues is a principal modification. Deamidation is one of the modifications of lens crystallins associated with aging and cataractogenesis. One proposed hypothesis of cataractogenesis is that it develops in response to altered surface charges that cause conformational changes, which, in turn, permit formation of disulfide bonds and crystallin insolubility. This report, showing deamidation among the disulfide bonded gamma S-crystallins from cataractous lenses, supports this hypothesis.     

Different mutations in the LMNA gene cause autosomal dominant and autosomal recessive Emery-Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy (EMD) is a condition characterized by the clinical triad of early-onset contractures, progressive weakness in humeroperoneal muscles, and cardiomyopathy with conduction block. The disease was described for the first time as an X-linked muscular dystrophy, but autosomal dominant and autosomal recessive forms were reported. The genes for X-linked EMD and autosomal dominant EMD (AD-EMD) were identified. We report here that heterozygote mutations in LMNA, the gene for AD-EMD, may cause diverse phenotypes ranging from typical EMD to no phenotypic effect. Our results show that LMNA mutations are also responsible for the recessive form of the disease. Our results give further support to the notion that different genetic forms of EMD have a common pathophysiological background. The distribution of the mutations in AD-EMD patients (in the tail and in the 2A rod domain) suggests that unique interactions between lamin A/C and other nuclear components exist that have an important role in cardiac and skeletal muscle function.     

The X-ray crystal structure of human gamma S-crystallin C-terminal domain.

gammaS-crystallin is a major human lens protein found in the outer region of the eye lens, where the refractive index is low. Because crystallins are not renewed they acquire post-translational modifications that may perturb stability and solubility. In common with other members of the betagamma-crystallin superfamily, gammaS-crystallin comprises two similar beta-sheet domains. The crystal structure of the C-terminal domain of human gammaS-crystallin has been solved at 2.4 A resolution. The structure shows that in the in vitro expressed protein, the buried cysteines remain reduced. The backbone conformation of the "tyrosine corner" differs from that of other betagamma-crystallins because of deviation from the consensus sequence. The two C-terminal domains in the asymmetric unit are organized about a slightly distorted 2-fold axis to form a dimer with similar geometry to full-length two-domain family members. Two glutamines found in lattice contacts may be important for short range interactions in the lens. An asparagine known to be deamidated in human cataract is located in a highly ordered structural region.     

Schistosoma mansoni: hycanthone/oxamniquine resistance is controlled by a single autosomal recessive gene.

Individual schistosomes of an hycanthone/oxamniquine-sensitive strain were crossed with individual schistosomes of the opposite sex and belonging either to the same sensitive population or to a different strain which exhibited high resistance to the two drugs. Schistosome crosses were performed by transfer of single worm pairs into the mesenteric veins of mice and the drug sensitivity/resistance of individual progeny worms was assessed using an in vitro test. Drug resistance behaved as an autosomal recessive trait, as shown by the results of the F1 and F2 generation and of the backcrosses. Drug-resistant worms appeared to be slightly less viable than their sensitive counterpart at all stages of the life cycle. The results are relevant for an interpretation of drug resistance and drug mechanisms and the approach used in this study may be applicable to different genetic markers in schistosomes.     

Chubby: a new autosomal recessive skeletal mutation producing dwarfism in the mouse

The chubby (cby) mutant is a previously undescribed skeletal mutation in the mouse. Breeding experiments showed that cby is a recessive mutant with complete viability, full penetrance and fertility in both sexes. Tests for allelism showed that the cby mutant is genetically unlike the somewhat similar mutants, stumpy (stm), pituitary dwarf (dw), spondylometaphyseal chondrodysplasia (smc), brachymorphic (bm), and achondroplasia (cn). The defects seem to occur mainly in growth cartilage. Microradiography revealed increased height of the epiphyseal growth plate and irregular bone trabeculae in the metaphysis. Light microscopy showed disturbed columnar organization of proliferative chondrocytes and pronounced signs of cellular disintegration. The hypertrophic zone, however, contained normally shaped chondrocytes arranged in regular columns. In spite of the normal cellular hypertrophy the pattern of cartilage mineralization was disturbed. The electron microscopy studies revealed very high amounts of matrix vesicles and numerous larger membrane coated structures in the extracellular matrix. Biochemical analysis of the affected growth cartilage revealed a slightly modified pattern of proteoglycan subpopulations and considerably longer chondroitin sulfate chains when compared with controls. From the present study it can be concluded that the cby mutant is a genetically and morphologically distinct condition with characteristic, somewhat rickets-like stigmata. The pathogenetic mechanism underlying the condition remains to be clarified.     

An autosomal recessive gene that delays expression of lupus in BXSB mice

We report the generation and serologic, cellular, histologic, and genetic characteristics of a BXSB/MpJScr substrain, termed BXSB/MpJScr-ll/ll, that has lost early-life male lupus disease. Classic genetic analysis suggested that delayed disease expression results from the action of a single autosomal recessive gene. This putative gene, referred to as ll (long-lived), causes a significant delay in expression of autoimmune serology (total serum IgG and anti-nuclear antibodies levels), monocytosis, and of immune complex-mediated histopathologic changes such as glomerulonephritis, arteritis, and myocardial infarction. Presumably as a consequence of the delayed immunopathology male BXSB/MpJScr-ll/ll mice live three to four times longer than regular BXSB/MpJScr. This strain might be useful for analysis of single genes responsible for severe autoimmune disease expression.     

The autosomal recessive nonsyndromic deafness locus DFNB72 is located on chromosome 19p13.3

We ascertained three consanguineous Pakistani families (PKDF291, PKDF335 and PKDF793) segregating nonsyndromic recessive hearing loss. The hearing loss segregating in PKDF335 and PKDF793 is moderate to severe, whereas it is profound in PKDF291. The maximum two-point LOD scores are 3.01 (D19S1034), 3.85 (D19S894) and 3.71 (D19S894) for PKDF291, PKDF335 and PKDF793, respectively. Haplotype analyses of the three families define a 1.16 Mb region of overlap of the homozygous linkage intervals bounded by markers D19S216 (20.01 cM) and D19S1034 (20.75 cM). These results define a novel locus, DFNB72, on chromosome 19p13.3. There are at least 22 genes in the 1.16 Mb interval, including PTPRS, ZNRF4 and CAPS. We identified no pathogenic variants in the exons and flanking intronic sequences of these three genes in affected members of the DFNB72 families. DFNB72 is telomeric to DFNB68, the only other known deafness locus with statistically significant support for linkage to chromosome 19p.