Mary L. Marazita

Gene mapping studies with the syndrome of autism

The UCLA Registry for Genetic Studies of Autism had collected data on 308 families by February 1, 1983. A subsample of 46 families withat least two affected children was analyzed for evidence of a Mendelian mode of inheritance. The data were consistent with an autosomal recessive mode of inheritance (Ritvo, E. R., Spence, M. A., Freeman, B. J. Mason-Brothers, A., Mo. A., and Marazita, M. L., 1985, American Journal of Psychiatry, in press). Thirty-four of these families were subjected to gene linkage analyses with 30 standard phenotypic gene markers. There is no evidence of linkage between the purported autism locus and HLA, either from analysis of HLA haplotype sharing or fromlod scores. In addition, close linkage with autism, i.e., ≤5% recombination, could be excluded for 19 of the other autosomal genetic markers. The largest positivelod score, 1.04, was with haptoglobin (HP), at recombination frequencies of 10% in males and 50% in females. Normal C-and Q-banded chromosome polymorphisms were evaluated for association with autism and as additional linkage markers.

Reevaluation of the chromosome 4q candidate region for early onset periodontitis

Evidence of linkage (lod=3.1, θ=0.05) was reported previously in one large kindred (the Brandywine genetic isolate) for an autosomal dominant form of early onset periodontitis (EOP) with a protein polymorphism in the vitamin D binding protein (GC) located on chromosome 4q12-q13. To evaluate the generality of this finding, 19 unrelated families (228 individuals), each with two or more EOP affected individuals, were ascertained and sampled. A restriction fragment length polymorphism (RFLP) at the GC locus and eight other polymorphic DNA markers and two red blood cell antigens located on proximal chromosome 4q in the vicinity of the GC locus were typed. Twelve genetic models of EOP were evaluated, which varied in diagnostic classification, penetrance, and mode of disease transmission. Results for all models strongly exclude linkage between an EOP susceptibility gene and this chromosomal region assuming locus homogeneity. Our data statistically exclude (lod≤ -2.0) the possibility that more than 40% of our families are linked to this candidate region for one model tested. Linkage under heterogeneity was excluded less strongly for other models, but no significant evidence in support of linkage was obtained for any model. Our results indicate that either the previous report of linkage was a false positive, or that there are two or more unlinked forms of EOP, with the form located in 4q12-q13 being less common.

Estimating the Recombination frequency for the PTC-Kell linkage

SummaryTwo data sets are analyzed for linkage between the PTC and Kell blood group loci. The original report of close linkage for these loci was that of Conneally et al. (1976), where the maximum likelihood estimate of Θ was 0.05. These two new data sets give a combined maximum likelihood estimate of

Genetic Linkage Analysis of Neurofibromatosis with DNA Markers

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Congenital central hypoventilation syndrome: Inheritance and relation to sudden infant death syndrome

m=f=0.28. Estimating the recombination frequency for the sexes separately gave

Cleft lip with or without cleft palate: Reanalysis of a three-generation family study from England

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