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Comment |
Rutledge E, et al 2001 reported that CLH-3, a CLC-2 anion channel ortholog, activated during meiotic
maturation in C-elegans oocytes.
CLC anion channels are ubiquitous and have been identified in
organisms as diverse as bacteria and humans. Despite their widespread
expression and likely physiological importance, the function and regulation of
most CLCs are obscure. The authors show by patch clamp electrophysiology that C. elegans oocytes
express a hyperpolarization- and swelling-activated Cl- current with
biophysical characteristics strongly resembling those of mammalian CLC-2.
Double-stranded RNA-mediated gene interference (RNAi) and single-oocyte RT-PCR
demonstrated that the channel is encoded by clh-3, one of six C. elegans CIC
genes. CLH-3 is inactive in immature oocytes but can be triggered by cell
swelling. However, CLH-3 plays no apparent role in oocyte volume homeostasis,
The physiological signal for channel activation is the induction of oocyte
meiotic maturation. During meiotic maturation, the contractile activity of
gonadal sheath cells, which surround oocytes and are coupled to them via gap
junctions, increases dramatically. These ovulatory sheath cell contractions
are initiated prematurely in animals in which CLH-3 expression is disrupted by
RNAi.
The inwardly rectifying Cl- current in C. elegans oocytes is due
to the activity of a CIC channel encoded by clh-3, Functional and structural
similarities suggest that CLH-3 and mammalian ClC-2 are orthologs. CLH-3 is
activated during oocyte meiotic maturation and functions in part to modulate
ovulatory contractions of gap junction-coupled gonadal sheath cells.
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