期刊
DEVELOPMENT
卷 133, 期 9, 页码 1657-1671出版社
COMPANY BIOLOGISTS LTD
DOI: 10.1242/dev.02341
关键词
left-right asymmetry; H+-V-ATPase; V-ATPase; Xenopus; chick; zebrafish; axial patterning; cytoplasmic pH; membrane voltage
资金
- NCRR NIH HHS [C06RR11244] Funding Source: Medline
- NIDCR NIH HHS [1-K22-DE016633-01A1, K22 DE016633, 1-T32-DE-08327, K22 DE016633-03] Funding Source: Medline
- NIGMS NIH HHS [1R01-GM-0622] Funding Source: Medline
Biased left-right asymmetry is a fascinating and medically important phenomenon. We provide molecular genetic and physiological characterization of a novel, conserved, early, biophysical event that is crucial for correct asymmetry: H+ flux. A pharmacological screen implicated the H+-pump H+-V-ATPase in Xenopus asymmetry, where it acts upstream of early asymmetric markers. Immunohistochemistry revealed an actin-dependent asymmetry of H+-V-ATPase subunits during the first three cleavages. H+-flux across plasma membranes is also asymmetric at the four- and eight-cell stages, and this asymmetry requires H+-V-ATPase activity. Abolishing the asymmetry in H+ flux, using a dominant-negative subunit of the H+-V-ATPase or an ectopic H+ pump, randomized embryonic situs without causing any other defects. To understand the mechanism of action of H+-V-ATPase, we isolated its two physiological functions, cytoplasmic pH and membrane voltage (V-mem) regulation. Varying either pH or V-mem, independently of direct manipulation of H+-V-ATPase, caused disruptions of normal asymmetry, suggesting roles for both functions. V-ATPase inhibition also abolished the normal early localization of serotonin, functionally linking these two early asymmetry pathways. The involvement of H+-V-ATPase in asymmetry is conserved to chick and zebrafish. Inhibition of the H+-V-ATPase induces heterotaxia in both species; in chick, H+-V-ATPase activity is upstream of Shh; in fish, it is upstream of Kupffer's vesicle and Spaw expression. Our data implicate H+-V-ATPase activity in patterning the LR axis of vertebrates and reveal mechanisms upstream and downstream of its activity. We propose a pH- and V-mem-dependent model of the early physiology of LR patterning.
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