A high-resolution recombination map of the human genome.

Determination of recombination rates across the human genome has been constrained by the limited resolution and accuracy of existing genetic maps and the draft genome sequence. We have genotyped 5,136 microsatellite markers for 146 families, with a total of 1,257 meiotic events, to build a high-resolution genetic map meant to: (i) improve the genetic order of polymorphic markers; (ii) improve the precision of estimates of genetic distances; (iii) correct portions of the sequence assembly and SNP map of the human genome; and (iv) build a map of recombination rates. Recombination rates are significantly correlated with both cytogenetic structures (staining intensity of G bands) and sequence (GC content, CpG motifs and poly(A)/poly(T) stretches). Maternal and paternal chromosomes show many differences in locations of recombination maxima. We detected systematic differences in recombination rates between mothers and between gametes from the same mother, suggesting that there is some underlying component determined by both genetic and environmental factors that affects maternal recombination rates.

Linkage of ischemic stroke to the PDE4D region on 5q in a Swedish population.

BACKGROUND AND PURPOSE: Recent Icelandic studies have demonstrated linkage for common forms of stroke to chromosome 5q12 and association between phosphodiesterase4D (PDE4D) and ischemic stroke. Using a candidate region approach, we wanted to test the validity of these findings in a different population from northern Sweden. METHODS: A total of 56 families with 117 affected individuals were included in the linkage study. Genotyping was performed with polymorphic microsatellite markers with an average distance of 4.5 cM on chromosome 5. In the association study, 275 cases of first-ever stroke were included together with 550 matched community controls. Polymorphisms were tested individually for association of PDE4D to stroke. RESULTS: Maximum allele-sharing lod score in favor of linkage was observed at marker locus D5S424 (lod score=2.06; P=0.0010). Conditional logistic regression calculations revealed no significant association of ischemic stroke to the defined at-risk allele in PDE4D (odds ratio, 1.1; 95% confidence interval, 0.84 to 1.45). A protective effect may though be implied for 2 of the polymorphisms analyzed in PDE4D. CONCLUSIONS: Using a candidate region approach in a set of stroke families from northern Sweden, we have replicated linkage of stroke susceptibility to the PDE4D gene region on chromosome 5q. Association studies in an independent nested case-control sample from the same geographically located population suggested that different alleles confer susceptibility/protection to stroke in the Icelandic and the northern Swedish populations.