DDX4 and cyst: We too observed abnormal spermatocyte cysts, and immunofluorescence studies using anti-Vasa to mark pre-meiotic germ cells enabled us to determine that, in addition to a loss of GSCs, the apical region of the testis contained cysts of spermatocytes (in positions where we would normally expect to find GSCs and spermatogonia) that contained variable numbers of cells, less than the normal number of 16 spermatocytes per cyst.