Hereditary sensory and autonomic neuropathy type II (HSANII) is an early-onset autosomal recessive disorder characterized by loss of perception to pain, touch, and heat due to a loss of peripheral sensory nerves. Mutations in hereditary sensory neuropathy type II (HSN2), a single-exon ORF originally identified in affected families in Quebec and Newfoundland, Canada, were found to cause HSANII. We report here that HSN2 is a nervous system-specific exon of the with-no-lysine(K)-1 (WNK1) gene. WNK1 mutations have previously been reported to cause pseudohypoaldosteronism type II but have not been studied in the nervous system. Given the high degree of conservation of WNK1 between mice and humans, we characterized the structure and expression patterns of this isoform in mice. Immunodetections indicated that this Wnk1/Hsn2 isoform was expressed in sensory components of the peripheral nervous system and CNS associated with relaying sensory and nociceptive signals, including satellite cells, Schwann cells, and sensory neurons. We also demonstrate that the novel protein product of Wnk1/Hsn2 was more abundant in sensory neurons than motor neurons. The characteristics of WNK1/HSN2 point to a possible role for this gene in the peripheral sensory perception deficits characterizing HSANII.
J. Neurochem. (2012) 120, 964–973.
Abstract
During pregnancy, activation of the maternal immune system results in inflammation in the foetal nervous system. The causative agents are pro‐inflammatory cytokines like interleukin‐1β (IL‐1β), produced by the foetus. In this study, we examine the effect of IL‐1β on the proliferation and differentiation of neural progenitor cells (NPCs) to better understand its potential effects on the developing brain. We find that the IL‐1β receptor (IL‐1R1) is expressed in the ventral mesencephalon of the developing brain. Furthermore, IL‐1R1 is expressed on Nestin‐positive, Sox‐2‐positive NPCs. IL‐1β treatment reduced the numbers of proliferating NPCs, an effect prevented by the IL‐1R1 receptor antagonist. LDH and MTT assays, and western blot analysis for cleaved caspase 3 and poly(ADP‐ribose) polymerase, confirmed that this was not due to an increase in cell death but rather an induction of differentiation. To further study the effects of IL‐1β on cell fate determination, we differentiated NPCs in the presence and absence of IL‐1β. Il‐1β promoted gliogenesis and inhibited neurogenesis, an effect that required p38‐MAPK kinase signalling. In summary, these data show that exposure of NPCs to IL‐1β affects their development. This necessitates an examination of the consequences that maternal immune system activation during pregnancy has on the cellular architecture of the developing brain.
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