BCL2L2 and Testicular atrophy: Mutation of BCL-w/BCL2L2 in a mouse strain resulted in male sterility and testicular degeneration associated with loss of Sertoli cells, highlighting an important role of BCL-w in testicular development and spermatogenesis.144,145 In addition, a role for BCL-w in B cell survival was reported, with loss of BCL-w leading to increased apoptosis upon growth factor withdrawal in B cells.146 Knockout of BCL2A1 has been technically challenging due to quadruplication of the gene locus in mice, which complicated conventional knockout studies.