Abstract
The With No lysine (K) family of serine/threonine kinase (WNK) defines a small family of kinases with significant roles in ion homeostasis. WNK1 has been shown to have different isoforms due to what seems to be largely tissue specific splicing. Here, we used two distinct in situ hybridization riboprobes on developing and adult mouse tissues to make a comparative analysis of Wnk1 and its sensory associated splice isoform, Wnk1/Hsn2. The hybridization signals in developing mouse tissues, which were prepared at embryonic day e10.5 and e12.5, revealed a homogenous expression profile with both probes. At e15.5 and in the newborn mouse, the two probes revealed different expression profiles with prominent signals in nervous system tissues and also other tissues such as kidney, thymus and testis. In adult mouse tissues, the two expression profiles appeared even more restricted to the nervous tissues, kidney, thymus and testis, with no detectable signal in the other tissues. Throughout the nervous system, sensory tissues, as well as in Cornu Ammonis 1 (CA1), CA2 and CA3 areas of the hippocampus, were strongly labeled with both probes. Hybridization signals were also strongly detected in Schwann and supporting satellite cells. Our results show that the expression profiles of Wnk1 isoforms change during the development, and that the expression of the Wnk1 splice variant containing the Hsn2 exon is prominent during developing and in adult mouse tissues, suggesting its important role in the development and maintenance of the nervous system.
Highlights
The With No K kinase (WNK) family of serine/ threonine protein kinases includes four members, WNK1 to WNK4, which are expressed in mammalian tissues
To test the expression profiles of Wnk1 and Wnk1/Hsn2 mRNA isoforms in developing and adult mouse tissues, we employed the in situ hybridization (ISH) technique
To prepare the vector encoding the sense and anti-sense Wnk1 ripoprobes, we used a mouse brain cDNA library and oligonucleotide primers that were designed to PCR amplify the 805 bp region located between the end of exon 1 to exon 6 of Wnk1
Summary
The With No K (lysine) kinase (WNK) family of serine/ threonine protein kinases includes four members, WNK1 to WNK4, which are expressed in mammalian tissues. WNK kinases regulate the activities of ion channels and cotransporters by modulating their trafficking and surface expression, as well as by influencing their signaling pathways [1,2]. The WNKs indirectly regulate salt retention in the kidney and ion balance in nervous tissues, suggesting diverse functional roles in the organism. It is proposed that the members of the WNK kinase family interact with each other and influence each other’s function [2]. A kidney specific, but kinase deficient variant of Wnk was proposed to have a tissue–specific promoter displaying tissue–specific expression [3]. Alternative skipping of exons 9, 11, 12, 26, 26a, 26b and Hsn of Wnk in a tissue–specific fashion and isoforms lacking exon 18 and 22 of Wnk were reported, but the physiological roles of these variants remain to be investigated [3,4,5,6,7]
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