Linked Life Data

9331337

Source:http://linkedlifedata.com/resource/pubmed/id/9331337

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1997-10-31
pubmed:databankReference
pubmed:abstractText
When treated with 17alpha,20beta-dihydroxy-4-pregnen-3-one (17alpha,20beta-DP), a natural maturation-inducing hormone in fishes, fully grown zebrafish oocytes are induced to mature via the activation of the maturation-promoting factor (MPF), which consists of cdc2 (a catalytic subunit) and cyclin B (a regulatory subunit). In contrast, 17alpha,20beta-DP is unable to induce growing (previtellogenic and vitellogenic) oocytes to mature. To know the reason growing oocytes fail to mature upon 17alpha,20beta-DP treatment, we investigated changes in the components of machinery responsible for MPF activation during zebrafish oogenesis. Immunoblotting experiments using monoclonal antibodies against cdc2, cyclin B, and cdk7 (an activator of cdc2) have revealed that the concentrations of cdc2 and cdk7 are almost constant during oogenesis. Cyclin B was present in mature oocytes but absent in growing and fully grown immature oocytes. These results, which are identical to those in goldfish, strongly suggest that cyclin B is synthesized from stored (masked) mRNA after 17alpha,20beta-DP stimulation and that its binding to the preexisting cdc2 allows cdk7 to activate MPF. Microinjection of cyclin B protein induced MPF activation and germinal vesicle breakdown in growing oocytes, as well as in fully grown oocytes, indicating that cdk7 present in growing oocytes is already active. Northern blot analysis revealed the presence of cyclin B mRNA in both previtellogenic and fully grown oocytes. These results indicate that, as in fully grown oocytes, growing oocytes are already equipped with the catalytic subunit of MPF (cdc2) and its activator (cdk7) and that the appearance of the regulatory subunit of MPF (cyclin B) is sufficient for initiating maturation. Therefore, the unresponsiveness of growing oocytes to 17alpha,20beta-DP is attributable to a deficiency in the processes leading to cyclin B synthesis, which include 17alpha,20beta-DP reception on the oocyte surface, subsequent signal transduction pathways, and unmasking the stored cyclin B mRNA.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0012-1606
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
190
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
142-52
pubmed:dateRevised
2009-11-19
pubmed:meshHeading
pubmed:year
1997
pubmed:articleTitle
Introduction of cyclin B induces activation of the maturation-promoting factor and breakdown of germinal vesicle in growing zebrafish oocytes unresponsive to the maturation-inducing hormone.
pubmed:affiliation
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't