AUTHOR=Jin Chunmei , Kang Hyae Rim , Kang Hyojin , Zhang Yinhua , Lee Yeunkum , Kim Yoonhee , Han Kihoon 

TITLE=Unexpected Compensatory Increase in Shank3 Transcripts in Shank3 Knock-Out Mice Having Partial Deletions of Exons

JOURNAL=Frontiers in Molecular Neuroscience

VOLUME=12

YEAR=2019

URL=https://www.frontiersin.org/journals/molecular-neuroscience/articles/10.3389/fnmol.2019.00228

DOI=10.3389/fnmol.2019.00228

ISSN=1662-5099

ABSTRACT=<p>Genetic variants of the SH3 and multiple ankyrin repeat domains 3 (<italic>SHANK3</italic>) gene, which encodes excitatory postsynaptic core scaffolds cause numerous brain disorders. Several lines of <italic>Shank3</italic> knock-out (KO) mice with deletions of different <italic>Shank3</italic> exons have previously been generated and characterized. The different <italic>Shank3</italic> KO mouse lines have both common and line-specific phenotypes. Shank3 isoform diversity is considered a mechanism underlying phenotypic heterogeneity, and compensatory changes through regulation of <italic>Shank3</italic> expression may contribute to this heterogeneity. However, whether such compensatory changes occur in <italic>Shank3</italic> KO mouse lines has not been investigated in detail. Using previously reported RNA-sequencing analyses, we identified an unexpected increase in <italic>Shank3</italic> transcripts in two different <italic>Shank3</italic> mutant mouse lines (<italic>Shank3B</italic> and <italic>Shank3ΔC</italic>) having partial deletions of <italic>Shank3</italic> exons. We validated an increase in <italic>Shank3</italic> transcripts in the hippocampus, cortex, and striatum, but not in the cerebellum, of <italic>Shank3B</italic> heterozygous (HET) and KO mice, using qRT-PCR analyses. In particular, expression of the N-terminal exons 1–12, but not the more C-terminal exons 19–22, was observed to increase in <italic>Shank3B</italic> mice with deletion of exons 13–16. This suggests a selective compensatory activation of upstream <italic>Shank3</italic> promoters. Furthermore, using domain-specific Shank3 antibodies, we confirmed that the increased <italic>Shank3</italic> transcripts in <italic>Shank3B</italic> KO mice produced a small Shank3 isoform that was not detected in wild-type mice. Taken together, our results illustrate another layer of complexity in the regulation of <italic>Shank3</italic> expression in the brain, which may also contribute to the phenotypic heterogeneity of different <italic>Shank3</italic> KO mouse lines.</p>