A rat H1t‐GFP transgene recapitulates endogenous H1t expression pattern in mouse

H1 histones bind to linker DNA. H1t (H1f6), a testis‐specific linker histone variant, is present in pachytene spermatocytes and spermatids. The expression of H1t histone coincides with the acquisition of metaphase I competence in pachytene spermatocytes. Here we report the generation of H1t‐GFP transgenic mice. The H1t‐GFP (H1 histone testis‐green fluorescence protein) fusion protein expression recapitulates the endogenous H1t expression pattern. This protein appears first in mid pachytene spermatocytes in stage V seminiferous tubules, persists in round spermatids and elongating spermatids, but is absent in elongated spermatids. The strong green fluorescence signal, due to the high abundance of H1t‐GFP, is maintained in spermatocytes after induction towards metaphase I through treatment with okadaic acid. Therefore, H1t‐GFP can be used as a visual marker for monitoring the progression of meiosis in vitro and in vivo, as well as fluorescence‐activated cell sorting (FACS) sorting of germ cells.