Non-syndromic mental retardation segregating with an apparently balanced t(1;17) reciprocal translocation through three generations

We describe a family in which nonsyndromic mental retardation (MR) and an a pparently balanced reciprocal translocation, t(1;17)(p36.3;p11.2) segregate s in eight individuals over three generations, Four children showed psychom otor developmental delay, reduced muscle tone, poor coordination, and learn ing difficulties. The affected adults had a varying range of behavioral pro blems and difficulties in social adjustment but no abnormal neurological si gns. Most of them were functioning at the borderline learning difficulty le vel in intellectual abilities with additional specific difficulties in read ing in two individuals. The Smith-Magenis and 1p36.3 deletion syndromes wer e excluded. We propose that this reciprocal translocation has disrupted an autosomal gene with an important function in cognitive development, and thi s family represents a unique resource for the molecular genetic study on no n-syndromic MR.(C) 2000 Wiley-Liss, Inc.