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Comment |
Alternative splicing of
fibronectin mRNA within three specific regions, the extra domains (ED) A and B
and the variable (V) or IIICS region, result in the production of different
isoforms of fibronectin. These isoforms differentially regulate tissue
developmental processes, such as those occurring during follicular and luteal
development. DeCandia LM, Rodgers RJ (REPRODUCTION FERTILITY AND DEVELOPMENT 11: 367-377 1999) characterized the expression of the alternative splicing
of the ED-A, ED-B and V regions of fibronectin mRNA in bovine
ovarian follicles and corpora lutea.
Bovine ovarian follicles (0.5-9 mm
diameter) and corpora lutea (cyclic, early to late mid-luteal phase) were
shown to express ED-A+, ED-A-, ED-B+, ED-B-, V+ and V- fibronectin isoforms,
similar to the liver, lung and kidney of fetuses, but generally not of adult
animals. Thus follicles and corpora lutea express isoforms of fibronectin
usually expressed in developing tissues.
//////Changes in the distribution of tenascin and fibronectin in the mouse ovary during folliculogenesis, atresia, corpus luteum formation and luteolysisYasuda K, et al .
Tenascin and fibronectin are components of the extracellular matrices that oppose and promote adhesion, respectively. Using immunohistochemical techniques, we studied the distribution of tenascin and fibronectin in the mouse ovary, in which dynamic reconstruction and degeneration occur during folliculogenesis, atresia, ovulation, corpus luteum formation and luteolysis. In growing follicles, tenascin was only detected in the theca externa layer, while fibronectin was detected in the theca externa layer, theca interna layer and basement membrane. During follicular atresia, granulosa cells, which are surrounded by the basement membrane, began to die through apoptosis. In atretic follicles, tenascin was detected in the basement membrane and theca externa layer. Distribution of fibronectin in atretic follicles was similar to that in healthy growing follicles, except that granulosa cells were slightly immunopositive for fibronectin. In young corpus luteum, luteal cells exhibit high 3 beta -hydroxysteroid dehydrogenase (3 beta -HSD) activity, an enzyme indispensable for progesterone production. Tenascin was barely detected in young luteal cells. 3 beta -HSD activity in luteal cells declines with corpus luteum age, and in older corpus luteum there is an increase in apoptotic death of luteal cells. Tenascin was intensely immunopositive in old luteal cells.In contrast, fibronectin immunostaining in luteal cells was relatively constant during corpus luteum formation and luteolysis. Our observations suggest that tenascin is critical in controlling the degenerative changes of tissues in mouse ovaries. Moreover, in all circumstances observed in this study, tenascin always co-localized with fibronectin, suggesting fibronectin is indispensable for the function of tenascin.
Distribution of extracellular matrix proteins type I collagen, type IV collagen, fibronectin, and laminin in mouse folliculogenesis. Berkholtz CB et al. The extracellular matrix (ECM) plays a prominent role in ovarian function by participating in processes such as cell migration, proliferation, growth, and development. Although some of these signaling processes have been characterized in the mouse, the relative quantity and distribution of ECM proteins within developing follicles of the ovary have not been characterized. This study uses immunohistochemistry and real-time PCR to characterize the ECM components type I collagen, type IV collagen, fibronectin, and laminin in the mouse ovary according to follicle stage and cellular compartment. Collagen I was present throughout the ovary, with higher concentrations in the ovarian surface epithelium and follicular compartments. Collagen IV was abundant in the theca cell compartment with low-level expression in the stroma and granulosa cells. The distribution of collagen was consistent throughout follicle maturation. Fibronectin staining in the stroma and theca cell compartment increased throughout follicle development, while staining in the granulosa cell compartment decreased. Heavy staining was also observed in the follicular fluid of antral follicles. Laminin was localized primarily to the theca cell compartment, with a defined ring at the exterior of the follicular granulosa cells marking the basement membrane. Low levels of laminin were also apparent in the stroma and granulosa cell compartment. Taken together, the ECM content of the mouse ovary changes during follicular development and reveals a distinct spatial and temporal pattern. This understanding of ECM composition and distribution can be used in the basic studies of ECM function during follicle development, and could aid in the development of in vitro systems for follicle growth.
Changes in mouse granulosa cell gene expression during early luteinization. McRae RS et al. Changes in gene expression during granulosa cell luteinization have been measured using serial analysis of gene expression (SAGE). Immature normal mice were treated with pregnant mare serum gonadotropin (PMSG) or PMSG followed, 48 h later, by human chorionic gonadotropin (hCG). Granulosa cells were collected from preovulatory follicles after PMSG injection or PMSG/hCG injection and SAGE libraries generated from the isolated mRNA. The combined libraries contained 105,224 tags representing 40,248 unique transcripts. Overall, 715 transcripts showed a significant difference in abundance between the two libraries of which 216 were significantly down-regulated by hCG and 499 were significantly up-regulated. Among transcripts differentially regulated, there were clear and expected changes in genes involved in steroidogenesis as well as clusters of genes involved in modeling of the extracellular matrix, regulation of the cytoskeleton and intra and intercellular signaling. The SAGE libraries described here provide a base for functional investigation of the regulation of granulosa cell luteinization.
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Comment |
Rodgers RJ et al reported the production of extracellular matrix, fibronectin and steroidogenic
enzymes, and growth of bovine granulosa cells in
anchorage-independent culture.
Zhao Y, et al 1995 reported gene expression and protein distribution of collagen, fibronectin and laminin in
bovine follicles and corpora lutea.
Colman-Lerner A, et al reported evidence for a role of the alternatively spliced ED-I sequence of
fibronectin (FN) during ovarian follicular development.
. Analysis of FN levels
in follicular fluids corresponding to different stages of development of bovine
follicles revealed marked changes in the concentrations of ED-I+ FN, whereas
total FN levels remained relatively constant. ED-I+ FN levels were higher in
small follicles, corresponding to the phase of granulosa cell proliferation. The
hypothesis of a physiological role for ED-I+ FN was further supported by the
finding of a regulation of the alternative splicing of FN in primary cultures of
bovine granulosa cells by factors known to control ovarian follicular
development. cAMP produced a 10-fold decrease in the relative proportion of the
ED-I region. In contrast, transforming growth factor-beta elicited a 2-fold
stimulation of overall FN synthesis and a 4-fold increase in the synthesis of ED-I
containing FN. This effect was evident at the protein (Western blots) and
messenger RNA (Northern blots) levels. A
possible mitogenic effect of ED-I+ FN was suggested by the observation that a
recombinant peptide corresponding to the ED-I domain stimulated DNA synthesis
in a bovine granulosa cell line (BGC-1), whereas a peptide corresponding to the
flanking type III sequences had no effect.
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