Parental transmission and D18S37 allele sharing in bipolar affective disorder.

We combined the five chromosome 18 bipolar affective disorder data sets provided by GAW10, totaling 185 families with 3,394 individuals, and performed analysis of differential parental transmission and chromosome 18 marker allele sharing in families with transmission through fathers vs those through mothers. Results indicated a significant excess of maternal transmission of bipolar disorder. All pedigrees were then broken into nuclear families and affected sib-pair linkage analyses performed on the marker, D18S37. There was significant linkage in the data overall, as well as in each subgroup of paternal, maternal and unknown parental transmission nuclear families. There were no significant differences in identical-by-descent (IBD) scores among the three transmission subgroups. These findings support an excess of maternal transmission, and linkage between bipolar disorder and marker D18S37. However, our results do not support the previous suggestion that there are differences in chromosome 18 marker allele sharing depending on the transmitting parent.