Methylauon of Unique Sequence Dna during Spermatogenesb in Mice

In order to study whether changes in methylation of unique sequence DNA were related to meiosis, DNA was pur i f ied from F9 embryonal carcinoma (a "primordial germ c e l l " equivalent) , germ ce l ls from immature testes (contain ing germ ce l ls up to early spermatocytes), sperm, and appropriate somatic t issues. Restr ict ion was performed with the isoschizomers Msp_ I and Hp£ I I , and Eco RI as a con t ro l . Electrophoresis and Southern transfers were followed by hybridizat ion to a mouse major (3-glob1n clone ( f 7 ) , a mouse pancreatic amylase clone (pMPa21), a type I , h istocompat ib i l i ty-2 clone (pH-2D-4), and a spermatid cDNA clone (pPM 459). The variably methylated si tes were a l l hypomethylated in the embryonal carcinoma DNA and hypermethylated in DNA from Immature testes and sperm, Irrespective of the t ranscr ip t ion state of the gene. The pattern in control tissues generally conformed to an inverse corre la t ion of methylation with t ranscr ip t ion . These results suggest that hypermethylation of sperm DNA persists from hypermethylation of these sequences early 1n tes t i cu la r development, independent of gene expression.