Evidence against GRB10 as the gene responsible for Silver-Russell syndrome

Recent evidence shows that Silver-Russell syndrome (SRS), the major functional deficit of which is limited growth, both intrauterine and postnatal, is due to a double dose of a gene within 7p11.2-p13 that is normally expressed exclusively from the maternal copy. Of the several growth-related genes in this chromosomal region, only GRB10 has been demonstrated to be imprinted; however, imprinting was limited to brain and muscle and was incomplete. Using reverse-transcript PCR, we now confirm GRB10 imprinting in these two tissues is isoform-specific and, more importantly, demonstrate absence of imprinting in growth plate cartilage, the tissue most directly involved in linear growth. Thus, it is unlikely that GRB10 is the gene responsible for SRS. (C) 2001 Academic Press.