Biology subjects

Azzi, C.

Publications and source records attributed to Azzi, C..

3 recordsLinked to original sources

bioRxiv2024

Protein degradation shapes developmental tempo in mouse and human neural progenitors

The pace of embryonic development differs markedly across mammalian species, yet the molecular mechanisms underlying these tempo differences remain largely unknown. Here, we systematically compared protein dynamics in mouse and human neural progenitors (NPs) and examined how protein stability influences developmental timing. We find that mouse NPs exhibit faster protein production and degradation than human NPs. Human NPs display broadly increased protein half-lives, independent of cellular compartment or protein function, and this difference persists in post-mitotic neurons. Consistent with this, proteasomal activity is lower in human embryonic spinal cord and stem cell-derived neural progenitors than mouse, correlating with reduced expression of proteasome-associated proteins. Functionally, accelerating the degradation of the key transcriptional repressor IRX3 in mouse NPs speeds the activation of its target gene, providing causal evidence that protein turnover modulates developmental tempo. These results reveal that species-specific regulation of protein degradation shapes the timing of neural development and suggest that evolutionary tuning of proteasomal activity contributes to differences in embryonic developmental pace.

developmental biology↗

bioRxiv2023

Convergence of multiple RNA-silencing pathways on GW182/TNRC6

The RNA-binding protein TRIM71/LIN-41 is a phylogenetically conserved developmental regulator that functions in mammalian stem cell reprogramming, brain development and cancer. TRIM71 recognizes target mRNAs through hairpin motifs and silences them through molecular mechanisms that await identification. Here, we uncover that TRIM71 silences its targets by recruiting TNRC6/GW182, a core component of the miRNA-induced silencing complex (miRISC). Co-immunoprecipitation reveals interaction of TNRC6A with additional RNA-binding proteins and we demonstrate that AGO2, TRIM71, and UPF1 each recruit TNRC6 to specific, largely distinct sets of transcripts to silence them. As cellular TNRC6 levels are limiting, competition occurs among the silencing pathways, such that loss of AGO2 protein, or of AGO2 binding to TNRC6, enhances the activities of the other pathways. We conclude that a miRNA-like silencing activity is shared among different mRNA silencing pathways and that use of TNRC6 as a central hub provides a means to integrate their activities.

molecular biology↗

bioRxiv2019

Two parallel arms of the heterochronic pathway direct coordinated juvenile-to-adult transition through distinct LIN-29 isoforms

Robust organismal development relies on temporal coordination of disparate physiological processes. In Caenorhabditis elegans, the timely transition from juvenile to adult is controlled by the heterochronic pathway, a regulatory cascade of conserved proteins and small RNAs. The heterochronic pathway culminates in accumulation of the transcription factor LIN-29, which triggers coordinated execution of juvenile-to-adult (J/A) transition events. Here, we reveal that two LIN-29 isoforms fulfill distinct functions during the J/A transition. We show that the functional differences between the isoforms do not stem from differences in their sequences, but from their distinct spatiotemporal expression, and we propose that distinct LIN-29 dose sensitivities of the individual J/A transition events help to ensure their temporal ordering. We demonstrate that unique lin-29 isoform expression patterns are generated by the RNA-binding protein LIN-41 for lin-29a, and the transcription factor HBL-1 for lin-29b. By regulating both HBL-1 and LIN-41, the RNA-binding protein LIN-28 coordinates LIN-29 isoform activity. Thus, our findings reveal that a coordinated transition from juvenile to adult involves branching of a linear pathway to achieve timely control of multiple events.

developmental biology↗