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M Johannes

Publications and source records attributed to M Johannes.

3 recordsLinked to original sources
PubMed2000

A new locus for autosomal dominant cataract on chromosome 12q13.

PURPOSE: To map the gene for autosomal dominant cataracts (ADC) in an American white family of European descent. METHODS: Ophthalmic examinations and linkage analyses using a variety of polymorphisms were performed; two-point lod scores calculated. RESULTS: Affected individuals (14 studied) exhibited variable expressivity of embryonal nuclear opacities based on morphology, location within the lens, and density. This ADC locus to 12q13 was mapped on the basis of statistically significantly positive lod scores and no recombinations (theta(m) = theta(f) = 0) with markers D12S368, D12S270, D12S96, D12S359, D12S1586, D12S312, D12S1632, D12S90, and D12S83; assuming full penetrance, a maximum lod score of 4.73 was calculated between the disease locus and D12S90. CONCLUSIONS: The disease in this family represents the first ADC locus on chromosome 12; major intrinsic protein of lens fiber (MIP) is a candidate gene.

Cataract↗
PubMed2000

A new betaA1-crystallin splice junction mutation in autosomal dominant cataract.

PURPOSE: To map the locus for autosomal dominant cataracts (ADCs) in a Brazilian family using candidate gene linkage analyses, describe the clinical variability, and identify potential mutations in the human betaA1-crystallin gene (CRYBA1), a candidate gene identified through linkage studies demonstrating cosegregation with markers on chromosome 17. METHODS: Members of a Brazilian family with ADC were studied. Clinical examinations and linkage analyses with polymerase chain reaction (PCR) polymorphisms of 22 anonymous markers and 2 within the neurofibromatosis type 1 gene were performed; two-point lod scores were calculated. DNA sequences of all 6 exons and 12 exon-intron boundaries of the betaA1-crystallin gene, a proximal candidate gene mapped to 17q11.1-q12 in one unaffected and two affected individuals, were screened and new variants assessed for cosegregation with the disease. RESULTS: Affected individuals exhibited variable expressivity of pulverulent opacities in the embryonal nucleus and sutures; star-shaped, shieldlike, or radial opacities in the posterior embryonal nucleus; and/or midcortical opacities. All known loci for ADC in this family on chromosomes 1 and 13 were excluded. A positive lod score on chromosome 17 was calculated. This ADC locus was mapped to two potential regions on the long arm with an intervening recombination. The only known candidate gene in these regions was betaA1-crystallin. Three previously unreported single nucleotide variants were found in this gene, one in the donor splice junction site of intron C. This variant was found in all affected members and is presumed to be the causative mutation. CONCLUSIONS: An ADC locus was mapped in a Brazilian family with variable expressivity to either 17q23.1-23.2 or 17q11.1-12 based on linkage analyses. Analyses of DNA sequences of the betaA1-crystallin gene in this family revealed three new variants, one of which is within a donor splice junction and cosegregates with affected members.

Base Sequence↗