The Will-o'-the-Wisp of Genetics — Hunting for the Azoospermia Factor Gene

It has been known for decades that the Y chromosome carries genes required for spermatogenesis and male fertility. But it has been frustratingly difficult to pin down the relevant genes, to such an extent that a finding reported by Luddi et al.1 in this issue of the Journal — that the ubiquitin-specific peptidase 9, Y-linked gene (USP9Y) is not essential for normal spermatogenesis — represents a noteworthy advance in the field.Approximately 15% of couples have difficulty conceiving; the causes are many and include genetic factors. The most common known genetic causes of spermatogenic failure are karyotype anomalies . . .