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General Comment |
Owens GE, et al 2002 reported the characterization of integrin expression in the mouse ovary.
Integrin alpha:beta heterodimers mediate cell contacts to the extracellular matrix and
initiate intracellular signaling cascades in response to a variety of factors. Integrins
interact with many determinants of cellular phenotypes and play roles in controlling
the development, structural integrity, and function of every type of tissue. To determine their
relevance to ovarian physiology, the authors have studied the expression of integrin subunit
mRNAs by Northern blot analysis and in situ hybridization in ovaries of wild-type,
growth differentiation factor 9 (Gdf 9) knockout, FSHbeta (Fshb) knockout, and
inhibin alpha (Inha) knockout mice.
Integrin beta(5), mRNA is predominantly expressed in granulosa
cells of multilayer follicles. It is expressed at high levels in the Fshb
knockout mice and in a compartmentalized manner in the granulosa cell/Sertoli
cell tumors that develop in the Inha knockout mice. Specific integrins are
associated with ovarian cellular phenotypes in mice, which raises intriguing
possibilities as to integrin functions in oocyte competence, follicular
development, luteinization, and granulosa cell proliferation.
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Comment |
Transcriptome profiling of granulosa cells of bovine ovarian follicles during growth from small to large antral sizes. Hatzirodos N 2014 et al.
BACKGROUND
At later stages of folliculogenesis, the mammalian ovarian follicle contains layers of epithelial granulosa cells surrounding an antral cavity. During follicle development granulosa cells replicate, secrete hormones and support the growth of the oocyte. In cattle, the follicle needs to grow > 10 mm in diameter to allow an oocyte to ovulate, following which the granulosa cells cease dividing and differentiate into the specialised cells of the corpus luteum. To better understand the molecular basis of follicular growth and granulosa cell maturation, we undertook transcriptome profiling of granulosa cells from small (< 5 mm; n = 10) and large (> 10 mm, n = 4) healthy bovine follicles using Affymetrix microarrays (24,128 probe sets).
RESULTS
Principal component analysis for the first two components and hierarchical clustering showed clustering into two groups, small and large, with the former being more heterogeneous. Size-frequency distributions of the coefficient of variation of the signal intensities of each probe set also revealed that small follicles were more heterogeneous than the large. IPA and GO enrichment analyses revealed that processes of axonal guidance, immune signalling and cell rearrangement were most affected in large follicles. The most important networks were associated with: (A) Notch, SLIT/ROBO and PI3K signalling, and (B) ITGB5 and extracellular matrix signalling through extracellular signal related kinases (ERKs). Upstream regulator genes which were predicted to be active in large follicles included STAT and XBP1. By comparison, developmental processes such as those stimulated by KIT, IHH and MEST were most active in small follicles. MGEA5 was identified as an upstream regulator in small follicles. It encodes an enzyme that modifies the activity of many target proteins, including those involved in energy sensing, by removal of N-acetylglucosamine from serine and threonine residues.
CONCLUSIONS
Our data suggest that as follicles enlarge more genes and/or pathways are activated than are inactivated, and gene expression becomes more uniform. These findings could be interpreted that either the cells in large follicles are more uniform in their gene expression, or that follicles are more uniform or a combination of both and that additional factors, such as LH, are additionally controlling the granulosa cells.
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