BRDT is an essential epigenetic regulator for proper chromatin organization, silencing of sex chromosomes and crossover formation in male meiosis
Fig 2
Depletion of BRDT does not affect the global DSB repair and synapsis of autosomes, but results in asynapsis of the sex chromosomes during pachynema.
(A-D, F-I) Chromosome spreads of wild type (WT) and Brdt-/- early and mid pachytene spermatocytes. Upper insets show an enlargement of the sex chromosomes. A schematic representation of each inset is shown below the original, with the X chromosome represented in purple and the Y chromosome in red. (A-D) Immunolocalization of γH2AX (green) and SYCP3 (red). (A, C) In both WT and Brdt-/- early pachytene spermatocytes, γH2AX is present in the sex chromosomes and as foci in the chromatin adjacent to the SC. (B, D) At mid pachynema, γH2AX is observed only in the X and Y chromosomes, including those in complete asynapsis (D, inset). (E) Quantification of sex chromosomes with synapsis defects at the PAR in WT (black bar) and Brdt-/- (grey bar) spermatocytes. Samples were obtained from three WT and Brdt-/- 3 month-old mice. n = 62 and 99 early pachytene, and 125 and 132 mid/ late pachytene WT and Brdt-/- spermatocytes respectively. **p<0.01, ***p<0.001. (F-I) Immunolocalization of SYCP1 (green) and SYCP3 (red). In WT early (F) and mid pachynema (G), all chromosomes are fully synapsed, including the sex chromosomes. (H-I) Brdt-/- spermatocytes exhibit fully synapsed autosomal bivalents, but numerous sex chromosomes are completely unsynapsed (I, inset).