Role of the imprinted allele of the Cdkn1c gene in mouse neocortical development

Yui Imaizumi,Yukiko Gotoh,Daichi Kawaguchi,Shohei Furutachi,Tomoyuki Watanabe,Hiroaki Miya

doi:10.1038/s41598-020-58629-9

Yui Imaizumi, Yukiko Gotoh + Show 4 more

Open Access

https://doi.org/10.1038/s41598-020-58629-9

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Abstract

Imprinted genes are expressed from only one allele in a parent of origin–specific manner. The cyclin-dependent kinase inhibitor p57kip2 is encoded by an imprinted gene Cdkn1c, with the paternal allele being silenced. The possible expression and function of the paternal allele of Cdkn1c have remained little studied, however. We now show that the paternal allele of the Cdkn1c gene is expressed at a low level in the developing mouse neocortex. Surprisingly, the central nervous system-specific conditional deletion of the paternal allele (pat cKO) at the Cdkn1c locus resulted in a marked reduction in brain size. Furthermore, pat cKO gradually reduced the number of neural stem-progenitor cells (NPCs) during neocortical development, and thus reduced the number of upper-layer neurons, which were derived from late-stage NPCs. Our results thus show that the paternal allele of the Cdkn1c locus plays a key role in maintenance of NPCs during neocortical development.

Highlights

Genomic imprinting refers to an epigenetic process that results in the inactivation of one of the two alleles of a gene in a parent of origin–dependent manner[1,2,3]
We first examined whether expression of the paternal allele of the Cdkn1c gene could be detected in the developing brain with the use of chimeric mice derived from a cross between lines—C57BL/6J (BL6) and JF1/Ms (JF1)—that differ with regard to single nucleotide polymorphisms (SNPs) at this locus
Immunohistochemical analysis previously showed that the amount of p57kip[2] (Cdkn1c) protein was reduced to an undetectable level in the brain by deletion of the maternal Cdkn1c allele[34], and reporter mice that allow monitoring of the expression of the paternal allele on the basis of the activity of firefly luciferase encoded by www.nature.com/scientificreports a construct knocked-in at this locus did not show a luminescence signal under normal dietary conditions[34]

Summary

Results

Expression of the paternal Cdkn1c allele in neocortical NPCs and neurons during mouse embryonic development. We examined expression of the paternal Cdkn1c allele in NPCs and neurons isolated from the neocortex of E16 embryos derived from a cross between BL6 male and JF1 female mice. We deleted the paternal allele in a CNS-specific manner by crossing BL6 Cdkn1cfl/fl male with BL6 Nestin-Cre+/− female mice and found that such deletion resulted in a substantial reduction in brain size apparent at postnatal day (P) 60 (Fig. 2a). This finding was unexpected given the low level of expression of the paternal allele compared with the maternal allele. To investigate the mechanism underlying the selective reduction in the number of upper layer neurons in the postnatal neocortex of paternal Cdkn1c cKO mice, we evaluated the production of deep layer and upper layer

E13 Control Cdkn1c pKO

E16 Control

Discussion