Chromatoid body integrates piRNA, SMG6 and m⁶A pathways to control mRNAs in the male germline

Ahmedani, A.; Savulkina, E.; Ma, L.; Champramary, S.; Pauli, A. D.; Valkonen, E.; Laasanen, S. O.; Palimo, R.; George, R. A.; Thapa, K.; Lehtiniemi, T.; Dicke, A.-K.; Kliesch, S.; Neuhaus, N.; Stallmeyer, B.; Tuttelmann, F.; Makela, J.-A.; Kotaja, N.

doi:10.64898/2026.03.26.714452

bioRxiv · 10.64898/2026.03.26.714452

Chromatoid body integrates piRNA, SMG6 and m⁶A pathways to control mRNAs in the male germline

Ahmedani, A.·Savulkina, E.·Ma, L.·Champramary, S.·Pauli, A. D.·Valkonen, E.·Laasanen, S. O.·Palimo, R.·George, R. A.·Thapa, K.·Lehtiniemi, T.·Dicke, A.-K.·Kliesch, S.·Neuhaus, N.·Stallmeyer, B.·Tuttelmann, F.·Makela, J.-A.·Kotaja, N.

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Abstract

Spermatogenesis requires tightly controlled transcriptome regulation, supported by the PIWI-interacting RNA (piRNA) and nonsense-mediated decay (NMD) pathways, both concentrated in the chromatoid body (CB) of haploid spermatids. We previously showed that the NMD endonuclease SMG6 interacts with the piRNA-binding protein PIWIL1, and that loss of either factor results in overlapping mRNA dysregulation, suggesting functional cooperation. Here, we demonstrate that SMG6 and PIWIL1 assemble with shared RNA-regulatory proteins and bind common mRNA targets in the testis. Functional experiments in GC-2spd cells revealed cooperative regulation of selected transcripts, including Ccny and Taf1d, and established that SMG6 is required for piRNA-guided degradation of these targets, implicating its endonuclease activity in the piRNA pathway. Target mRNAs were mA-methylated, and this modification shaped their expression levels, SMG6 binding, and CB localization. Moreover, intact target mRNAs accumulated in CBs isolated from Smg6-cKO testes, indicating defective CB-associated decay. Together, these findings uncover a key role for the CB in mRNA regulation through coordinated action of the NMD and piRNA pathways.

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Ahmedani, A., Savulkina, E., Ma, L., Champramary, S., Pauli, A. D., Valkonen, E., Laasanen, S. O., Palimo, R., George, R. A., Thapa, K., Lehtiniemi, T., Dicke, A.-K., Kliesch, S., Neuhaus, N., Stallmeyer, B., Tuttelmann, F., Makela, J.-A., Kotaja, N.. 2026-03-28. Chromatoid body integrates piRNA, SMG6 and m⁶A pathways to control mRNAs in the male germline. https://doi.org/10.64898/2026.03.26.714452

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