2 Possible importance of low molecular weight se-cretions
New concepts of sperm function have evolved from several transgenic mouse models in which male inferti-lity stems from a specific sperm morphology: flagellar angulation. This is rare in normal mice [5], but was no-ticed first in many transgenic mice displaying male infer-tility together with normal testicular sperm production.The first to be reported was the c-ros (a proto-oncogene)knockout mouse [6, 7], but was followed by a natural murine mutant of SHP1 (a phosphatase that dephospho-rylates phosphorylated c-ros) [8], the transgenic GPX5Tag2 mouse [9] (where the T-antigen is targeted to the caput epididymidis by the caput-specific GPX5 gene promoter), the Apolipoprotein E receptor 2(ApoER2) knockout mouse [10] (which lacks testicular selenium uptake [11]), the Foxi1 (forkhead transcription factor) knockout mouse [12] and the LRG4 (GPCR)hypo-mutant mouse [13].