Genes for Sperm‐specific Basic Nuclear Proteins in Bufo and Xenopus Are Expressed at Different Stages in Spermatogenesis

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Abstract
The expression of the genes for sperm-specific basic nuclear proteins was examined, using the cDNA clones encoding protamine (P2) of Bufo japonicus and SP4 of Xenopus laevis as probes. Northern analyses showed that the mRNAs for these proteins were present only in the testes. Analyses with total RNA extracted from testicular cells at various spermatogenic stages revealed that in Bufo the transcripts of protamine genes are present in the spermatids, while in Xenopus the mRNAs for SP4 are present in both primary spermatocytes and spermatids. In situ hybridization studies with radiolabeled antisense RNA probes generated from cDNAs indicated that the Bufo protamine mRNAs accumulated first in round spermatids, while the Xenopus SP4 mRNAs did so in the pachytene stage of primary spermatocytes and thereafter.