The Generation of Alternative Transcripts as a Means of Regulating Phosphorylation in Sonic Hedgehog Medulloblastoma

Protein phosphorylation is critical in development and tumor progression; however, the promiscuity of kinases often limits the ability to regulate phosphorylation events selectively. Co- and post-transcriptional mechanisms, such as alternative transcription start site (ATSS) usage and alternative splicing (AS), may generate isoforms that include or exclude exons harboring critical phosphorylation sites, offering a potential mechanism for regulation at the mRNA level. The sonic hedgehog (SHH) subtype of medulloblastoma (MB), the most common malignant pediatric cerebellar tumor, arises from granule neuron precursors (GNPs) through aberrant SHH signaling. Murine postnatal day 7 (P7) GNPs are highly proliferative and share strong molecular and transcriptomic similarities with MB, providing an ideal model to study phosphorylation dynamics in tumors and their developmental precursors. Here, we investigated the regulation of phosphorylation at the transcript level in P7 GNP and MB. We integrated phosphoproteomic, whole-cell proteomic, and RNA sequencing (RNA-Seq) datasets from murine P7 GNPs and Ptch1+/− MBs to identify 12 candidate genes exhibiting isoform-level differences in phosphorylation. Among these, Ring Finger Protein 220 (Rnf220) and Septin-9 (Sept9) emerged as key candidates, with their longer phosphorylated isoforms showing significantly higher expression in MB compared to GNP. At the protein level, the Sept9 long isoform was found to localize preferentially to the periphery of MB cells, suggesting a potential isoform-specific role in the spatial organization or compartmentalization of tumor cells. These findings support a biological model in which alternative transcript usage regulates the inclusion of phosphorylation sites at the mRNA level, representing a novel layer of transcriptional control to regulate phosphorylation in cellular processes.

Department dc:contributor.department

Translational Medicine

Year dc:date.issued

2025

Author dc:creator

• Ogawa. Kana

Advisors dc:contributor.supervisor

• Purzner, Teresa
• Purzner, James

• Sonic Hedgehog Medulloblastoma
• Granule Neuron Precursors
• Phosphorylation
• Alternative Splicing
• Alternative Transcription Start Sites

Statement dc:rights

• Attribution-NonCommercial-NoDerivatives 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc-nd/4.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1974/35284

OAI identifier oai:identifier

oai:queensu.scholaris.ca:1974/35284