DDC (dopa decarboxylase) lies 27 kb from GRB10,
an imprinted gene implicated in Silver-Russell
syndrome. In an association study between
bipolar affective disorder and a DDC allele with a 4 bp deletion polymorphism (in a neuronally
untranslated exon), 100 case-parent trios indicated preferential paternal transmission (P = 0.006),
suggesting a parent of origin effect (Borglum
AD et al, 2003). Previous studies have shown that although there is evidence of asynchronous
replication of DDC, expression analysis shows biallelic expression of DDC in various human (brain,
eye, tongue, gut, kidney, liver, lung, skin, placenta) and mouse (brain, liver, kidney) tissues (Hitchins
MP et al, 2002).
Imprinting of the exon 1a transcript of mouse Ddc has now been documented
in mouse heart (Menheniott
TR et al, 2007).