Minotaur is critical for primary piRNA biogenesis

Area of Science:

• Reproductive Biology
• Molecular Genetics
• Epigenetics

Background:

• Piwi proteins and PIWI-interacting RNAs (piRNAs) are vital for animal fertility, primarily by silencing mobile genetic elements to protect germline genomes.
• piRNA clusters encode the information for piRNA production, which involves processing long primary transcripts into mature piRNAs.
• Mechanisms governing piRNA biogenesis and the definition of piRNA-producing loci remain incompletely understood.

Purpose of the Study:

• To investigate the genetic basis of fertility defects and identify novel components of the piRNA pathway.
• To elucidate the role of CG5508, a glycerol-3-phosphate O-acetyltransferase (GPAT) family member, in piRNA biogenesis.

Main Methods:

• Screening of an EMS-mutant collection with annotated fertility phenotypes to identify genes involved in the piRNA pathway.
• Characterization of a specific mutant strain exhibiting transposon-silencing defects and impaired primary piRNA biogenesis.
• Functional analysis of the CG5508 gene, including assessment of a catalytically inactive mutant, in piRNA biogenesis.

Main Results:

• Twenty-seven homozygous sterile strains displayed transposon-silencing defects.
• A mutation in CG5508 was identified as the cause of severe defects in primary piRNA biogenesis.
• A catalytically inactive mutant of CG5508 retained function in piRNA biogenesis, suggesting a non-enzymatic role.

Conclusions:

• The gene CG5508, now named Minotaur, is essential for primary piRNA biogenesis and transposon silencing.
• Phospholipid signaling, potentially through GPAT enzymes, plays a role in the piRNA pathway.
• Minotaur functions in piRNA biogenesis independently of its enzymatic activity, indicating a novel role in the pathway.