A general autosomal/X-linked model

This paper describes a general genetic model which encompasses both autosomal and X-linked inheritance as submodels. It allows one to test for X-linked inheritance of a trait by comparing the likelihood of X-linked inheritance to the likelihood of the general genetic model. The general model is formulated as two loci, the first representing the trait locus and the second representing the sex chromosomes. The test for X-linked inheritance is a test of linkage between the two loci. Three data sets were analyzed using this approach. Each was also analyzed using a variant of a model introduced by Demenais and Elston [1981], which treats the transmission probabilities as estimable parameters. Similar conclusions were reached using either model.

The inheritance of immunoglobulin E: genetic linkage analysis

Linkage analyses between 21 genetic markers including HLA-A, B, and the postulated locus for determining total serum IgE levels were done to try to clarify the inheritance of total IgE levels and to map the locus. A total of 316 individuals from five Mormon kindreds were studied, and data from an additional 204 Amish individuals from 11 families were analyzed for possible HLA linkage. Segregation analyses of both data sets did not give clear definition of the mode of inheritance of total IgE levels, but purely environmental models were rejected. Linkage analyses gave significant evidence against HLA linkage with the codominant, recessive, or dominant model of inheritance for total IgE levels. No significant evidence for linkage with any of the genetic markers was obtained. Since total serum IgE levels are correlated with allergies, understanding the genetics of total IgE levels is important to understanding the genetics of allergic disease in man.

X-linked inheritance of Alport syndrome: family P revisited

Likelihood analysis using two autosomal/X-linked mixed models confirmed that Alport syndrome is an X-linked dominant disease in a large Utah kindred, family P. The penetrance was estimated as .85 in females and 1.0 in males. Previously reported abnormal segregation ratios were reexamined. No excess of affected offspring of affected parents was found. Nor was the penetrance in daughters of asymptomatic carrier mothers found to be lower than in the daughters of symptomatic mothers, although the sample size was small. However, there was an unexplained deficiency of sons of affected fathers. There was no deficiency of sons of affected mothers, nor was there a deficiency of males in the kindred.

The genetics of quantitative plasma Lp(a): analysis of a large pedigree

Likelihood analysis using the mixed model of quantitative plasma Lp(a) measurements on members of a large pedigree provided evidence that high levels of Lp(a) are inherited as a dominant major gene with polygenic background. The dominant allele frequency was estimated as 0.10. The major gene and polygenic components together accounted for 95% of the variation seen in the measurements. The major gene index and OBP plots, methods that do not allow for the presence of both components, favored the polygenic model over the major gene model as the mode of inheritance. No association was found with any of the lipids, lipoproteins or apolipoproteins considered.

Inheritance of immunoglobulin E: genetic model fitting

Total serum immunoglobulin E (IgE) concentration was measured on 316 members of five pedigrees selected through breast cancer probands. Sex- and age-adjusted natural logarithm-transformed IgE level was not found to differ between individuals with breast cancer or with cancer of any site and other relatives. Likelihoods of the polygenic and of one-locus, two-allele major gene and mixed models were computed. The analysis provided evidence for the presence of a polygenic component in the determination of IgE; it did not show evidence of a major gene effect.

Spinal dysraphia as an autosomal dominant defect in four families

Four families were selected randomly on the basis of the occurrence of spina-bifida cystica and/or spina bifida occulta in one or more family members. Sixty-three relatives were studied clinically and roentgenologically; their roentgenograms were evaluated blindly. Twenty-eight were clinically and roentgenologically normal; 35 were diagnosed as having spina bifida occulta (SBO), spina bifida cystica (SBC), vertebral anomalies, and/or external defects usually interpreted as evidence for SBO. Excluding one proband we found the frequency of SBO to be 19/51 (37%) and the frequency of all types of spinal/vertebral defects (excluding five probands) to be 30/58 (52%). The distribution of these defects in the four families was analyzed using likelihood methods corrected for random ascertainment. The log likelihood values for sporadic, recessive, and dominant models were -26.69, -20.95, and -18.90, respectively, indicating a higher likelihood of autosomal dominant inheritance than sporadic occurrence or recessive inheritance. The penetrance probability in this dominant model, estimated by maximum likelihood, is 0.749 +/- 0.100. Further examination of these data suggest that SBO and SBC represent different expressions of the same dominant gene in these kindreds.

Hereditary myeloperoxidase deficiency

Subjects with neutrophil myeloperoxidase (MPO) deficiency have been rarely reported. In part this may be due to the lack of a simple screening technique that would detect them. With the routine use of a cytochemical leukocyte differential counter that employs MPO stains, over a 40-mo a period 8 unrelated probands with partial MPO-deficiency and one with complete deficiency were identified. Family studies have identified 23 additional, partially deficient subjects. The largest pedigrees demonstrate that the carrier state or partial MPO deficiency is inherited in an autosomal dominant pattern. Leukocytes from a subject with complete MPO deficiency and from some subjects with partial deficiency have impaired bactericidal activity against S. aureus. Superoxide generation was increased and chemiluminescence decreased in MPO-deficient leukocytes. Eleven subjects were prospectively followed for 18-30 mo. Only two partially deficient subjects have had serious infections consisting of recurrent streptococcal cellulitis and aseptic meningitis. These data suggest that leukocyte MPO deficiency is a common inherited defect that results in minimal clinical problems, supporting the concept of multiple leukocyte bacterial killing systems.

Analysis of a large pedigree with elliptocytosis, multiple lipomatosis, and biological false-positive serological test for syphilis

Elliptocytosis, multiple lipomatosis, and biological false-postive serological test for syphilis (BFPSTS) were found in a single individual. One hundred eighty relatives were tested for the three diseases: 74 were typed for seven blood group antigens, and 58 were typed for four electrophoretic enzyme markers. Likelihood analysis of the pedigree data confirmed independent dominant inheritance for elliptocytosis and lipomatosis. BFPSTS appears dominant, but the analysis was inconclusive. No linkages were found between any disease gene and any marker gene. Two female pedigree members with BFPSTS developed systemic lupus erythematosus, a finding in agreement with the previously described association. The analysis did not lead to any conclusions about the causal relationship between the two traits.