Mutations in noncoding regions of the proteolipid protein gene in Pelizaeus-Merzbacher disease.

BACKGROUND: Pelizaeus-Merzbacher disease (PMD) is an X-linked recessive dysmyelinating disorder of the CNS. Duplications or point mutations in exons of the proteolipid protein (PLP) gene are found in most patients. OBJECTIVE: To describe five patients with PMD who have mutations in noncoding regions of the PLP gene. METHODS: Quantitative multiplex PCR and Southern blot analyses were used to detect duplication of the PLP gene, and DNA sequence analysis, including exon-intron borders, was used to detect mutation of the PLP gene. RESULTS: Duplication of the PLP gene was ruled out, and mutations were identified in noncoding regions of five patients in four families with PMD. In two brothers with a severe form of PMD, a G to T transversion at IVS6+3 was detected. This mutation resulted in skipping of exon 6 in the PLP mRNA of cultured fibroblasts. A patient who developed nystagmus at 16 months and progressive spastic ataxia at 18 months was found to have a 19-base pair (bp) deletion of a G-rich region near the 5' end of intron 3 of the PLP gene. A patient with a T to C transition at IVS3+2 and a patient with an A to G transition at IVS3+4 have the classic form of PMD. These, like the 19-bp deletion, are in intron 3, which is involved in PLP/DM20 alternative splice site selection. CONCLUSIONS: Mutations in introns of the PLP gene, even at positions that are not 100% conserved at splice sites, are an important cause of PMD.

Segregation and linkage analysis of the complex trait Q1.

Segregation and linkage analysis of GAW9 Problem 2 quantitative trait 1 (Q1) was performed. Eight segregation models comprising all possible combinations of the environmental factor (EF), quantitative trait 2 (Q2), and quantitative trait 3 (Q3) as covariates were considered. Seven of the eight segregation models showed strong evidence for a major gene, the other model was marginal. When all genotypes are known, some evidence for linkage (lod > 2) was found to all three of the markers that affect Q1. Furthermore, four of the eight models each showed some linkage (lod > 2) to two of the three markers that affect Q1 with no false positives. Each of these segregation analysis major genes is a hybrid combination of the true multiple loci that affect Q1.

Conservation of human chromosome 18 in baboons (Papio hamadryas): a linkage map of eight human microsatellites.

A panel of 25 microsatellite loci known to map to human chromosome 18 was screened for length polymorphisms in a multigenerational pedigree of baboons (Papio hamadryas). Eight of these loci were polymorphic in the baboon pedigrees, with observed heterozygosity values ranging from 0.16 to 0.88. All eight loci show strong evidence of linkage. The most likely map order among the microsatellite loci for Papio is completely compatible with the locus order found in the human genome, and sex differences in recombination rates are also similar in the two species. We conclude that the organization of the chromosomal region defined by these loci is largely conserved between baboons and humans.