Gene expression profiling of human GV oocytes: an analysis of a profile obtained by Serial Analysis of Gene...

A gene expression profile of the human GV oocyte has recently been established by Serial Analysis of Gene Expression (SAGE). A significant number of the genes identified in this profile had not previously been associated with mammalian oocytes. We sought to confirm gene matches by RT-PCR amplification of candidate transcripts using mouse eggs. Attention focused on receptors, proteins involved in apoptosis, and cytoskeletal proteins. Two receptors found in the human catalogue, CCR6 and PAR3, were not found in mouse eggs, whereas myosin light chain, LLGL, beta-actin, 5HT receptor, bad, bak, DFF45, and Caspase homologue (cash) were. Individual SAGEtags can match more than one gene and, in some cases, more than ten. Examination of transcript sequences that generate multiple gene assignments identified a common denominator of short interspersed elements or Alu sequences. For reasons which are, as yet, unclear, the human GV oocyte SAGE catalogue contains relatively high abundances of SAGEtags in Alu sequences. This may reflect normal expression of Alu-containing genes in eggs or upregulated expression of Alu elements following stress. The degeneracy of gene matches in SAGE generated by Alu sequences makes independent confirmation of candidate genes essential.