Isoform switch of T-cell factor7L2 during mouse heart development

Area of Science:

• Cardiovascular Biology
• Molecular Biology
• Gene Regulation

Background:

• Canonical WNT signaling is crucial for heart development and disease, but its context-specific mechanisms are not fully understood.
• Tcf7l2 (TCF/LEF transcription factor 7-like 2) is a key nuclear effector of WNT signaling, interacting with β-catenin.
• Alternative splicing of Tcf7l2 transcripts is hypothesized to contribute to WNT signaling specificity in cardiac tissues.

Purpose of the Study:

• To investigate the role of Tcf7l2 alternative splicing in mediating WNT signaling specificity within the developing and postnatal heart.
• To identify and characterize different Tcf7l2 isoforms present in mouse ventricular tissues at embryonic and postnatal stages.

Main Methods:

• Cloning and sequencing of Tcf7l2 transcripts from embryonic day 17.5 and postnatal day 8 mouse ventricular tissues.
• Analysis of alternative splicing patterns, focusing on exon usage and variations in C-terminal exons.
• Reverse transcription polymerase chain reaction (RT-PCR) to validate splicing patterns across multiple developmental stages.

Main Results:

• Identification of 32 distinct Tcf7l2 isoforms from 53 sequenced transcripts, with significant variations in exon 4, 6, and 17 usage.
• Alternative splicing was prominent in C-terminal exons (14, 15, 16), with exon 14 inclusion increasing significantly from embryonic to postnatal stages.
• Exon 14 insertion created a redox-switch domain, and adenine indels near exon 18 altered isoform structures, affecting key functional motifs and driving isoform transitions (E, S, M).

Conclusions:

• Tcf7l2 alternative splicing generates diverse protein isoforms with distinct functional domains, impacting WNT signaling pathways.
• A postnatal, redox-sensitive switch in Tcf7l2 isoforms occurs, potentially regulating cardiomyocyte maturation.
• These findings provide insights into the context-dependent mechanisms of WNT signaling in cardiac development and disease.