Comparison of genome architecture at two stages of male germline cell differentiation in Drosophila

Eukaryotic chromosomes are spatially segregated into topologically associating domains (TADs), some of them being attached to the nuclear lamina (NL) in lamina-associated domains (LADs). Here, we identified LADs and TADs at two consecutive stages of Drosophila spermatogenesis – in spermatogonia (SpG) and spermatocytes (SpCs). We found that launching of SpC-specific transcription frequently correlates with promoters' detachment from the NL accompanied by spatial insulation of adjacent regions. We also revealed an increased contact frequency between SpC-specific genes implying their de novo gathering into “transcription factories”. In SpG and SpCs, single X chromosome is stronger associated with the NL than autosomes. Nevertheless, active chromatin regions in the X chromosome interact with each other more frequently than in autosomes. Moreover, despite the absence of dosage compensation complex in the male germline, randomly inserted SpG-specific reporter is expressed higher in the X chromosome than in autosomes, thus evidencing that non-canonical dosage compensation operates in SpG. Overall design: Hi-C analysis of chromatin spatial structure in Drosophila male germline cells at two consequitive stages of differentiation.