Ank1 (P2) KO mouse: transcriptomic analysis and evaluation of Nek5 gene expression

Studies in the past years in our laboratory have focused on sAnk1.5, a muscle-specific ankyrin isoform involved in stabilizing the sarcoplasmic reticulum around myofibrils. sAnk1.5 transcription is driven by the internal, skeletal muscle-specific P2 promoter of the Ankyrin 1 (Ank1) gene, specifically located within the intron between exons 39 and 40. The P2 promoter also directs the expression of a striated muscle-enriched microRNA, namely miR-486. Initial studies of a knockout mouse model (Ank1 (P2) KO) carrying a deletion that encompasses the P2 promoter confirmed that these mice lack sAnk1.5 and exhibit significantly reduced levels of miR-486, and revealed that lack of sAnk1.5 in these mice results in destabilization of the sarcoplasmic reticulum around the myofibrils. More recent studies have demonstrated that the Ank1 (P2) KO mice display increased fasting glucose levels and impaired glucose tolerance. Notably transgenic expression of sAnk1.5 and miR-486 in the Ank1 (P2) KO mice does not restore normal glucose homeostasis indicating that this is not strictly dependent on the lack of sAnk1.5 and on the reduction of miR-486 expression. This suggests that the observed hyperglycaemic phenotype is not due to the loss of the two P2 promoter-mediated expression of sAnk1.5 and miR-486, but it may rather reflect a broader effect caused by the deletion in this genomic region. To identify the molecular pathways driving this altered glucose homeostasis, we performed a transcriptomic analysis of extensor digitorum longus (EDL), soleus, and tibialis anterior (TA) muscles from Ank1 (P2) KO mice. Interestingly, while just the expression of few genes was modestly, albeit significantly, altered in the Ank1 (P2) KO mice, only the expression of the Nek5 gene was drastically reduced in these mice. Consequently, we proceeded with a more thorough characterization of Nek5 expression in WT and Ank1 (P2) KO mice.