Spectrum of mutations that cause distal arthrogryposis types 1 and 2B.

The distal arthrogryposis (DA) syndromes are a group of disorders characterized by non-progressive congenital contractures of the limbs. Mutations that cause distal arthrogryposis syndromes have been reported in six genes, each of which encodes a component of the contractile apparatus of skeletal myofibers. However, these reports have usually emanated from gene discovery efforts and thus potentially bias estimates of the frequency of pathogenic mutations at each locus. We characterized the spectrum of pathogenic variants in a cohort of 153 cases of DA1 (n = 48) and DA2B (n = 105). Disease-causing mutations in 56/153 (37%) kindreds including 14/48 (29%) with DA1 and 42/105 (40%) with DA2B were distributed nearly equally across TNNI2, TNNT3, TPM2, and MYH3. In TNNI2, TNNT3, and TPM2 the same mutation caused DA1 in some families and DA2B in others. We found no significant differences among the clinical characteristics of DA by locus or between each locus and DA1 or DA2B. Collectively, the substantial overlap between phenotypic characteristics and spectrum of mutations suggests that DA1 and DA2B should be considered phenotypic extremes of the same disorder.

Alterations in the ovarian transcriptome during primordial follicle assembly and development.

The assembly of the developmentally arrested primordial follicle and subsequent transition to the primary follicle are poorly understood processes critical to ovarian biology. Abnormal primordial follicle development can lead to pathologies such as premature ovarian failure. The current study used a genome-wide expression profile to investigate primordial follicle assembly and development. Rat ovaries with predominantly unassembled, primordial, or primary follicles were obtained. RNA from these ovaries was hybridized to rat microarray gene chips, and the gene expression (i.e., ovarian transcriptome) was compared between the developmental stages. Analysis of the ovarian transcriptome demonstrated 148 genes up-regulated and 50 genes down-regulated between the unassembled and primordial follicle stages. Observations demonstrate 80 genes up-regulated and 44 genes down-regulated between the primordial and primary follicle stages. The analysis demonstrated 2332 genes common among the three developmental stages, 146 genes specific for the unassembled follicles, 94 genes specific for the primordial follicles, and 151 genes specific for the primary follicles. Steroidogenic genes are up-regulated between unassembled and primordial follicles, and then many are again down-regulated between primordial and primary follicles. The hormones inhibin and Mullerian inhibitory substance (MIS) display a similar pattern of expression with the highest levels of mRNA in the primordial follicles. Several novel unknown genes that had dramatic changes in expression during primordial follicle development were also identified. Gene families/clusters identified that were up-regulated from unassembled to primordial follicles include growth factors and signal transduction gene clusters, whereas a down-regulated gene family was the synaptonemal complex genes associated with meiosis. Gene families/clusters that were up-regulated between primordial and primary follicles included immune response genes, metabolic enzymes, and proteases, whereas down-regulated gene families include the globulin genes and some steroidogenic genes. The expression of several growth factors changed during primordial follicle development, including vascular endothelial growth factor and insulin-like growth factor II. Elucidation of how these changes in gene expression coordinate primordial follicle assembly and the primordial to primary follicle transition provides a better understanding of these critical biological processes and allows selection of candidate regulatory factors for further investigation.

Insulin but not insulin-like growth factor-1 promotes the primordial to primary follicle transition.

A critical step in ovarian biology is the transition of the developmentally arrested primordial follicle to the growing primary follicle. The current study utilizes a rat ovarian organ culture system to investigate the role of insulin and insulin-like growth factor-1 (IGF-1) in this process. Four-day-old rat ovaries were cultured and the degree of primordial to primary follicle transition measured. Insulin increased the primordial to primary follicle transition 30% over control with a half maximal effective concentration (EC50) between 2.5 and 5 ng/ml. IGF-1 did not cause an increase in the primordial to primary follicle transition at concentrations up to 100 ng/ml. Ovaries were also treated with epidermal growth factor (EGF) and hepatocyte growth factor (HGF) and neither had an effect on the primordial to primary follicle transition. Ovaries were treated with insulin in conjunction with other factors known to promote the primordial to primary follicle transition in order to discern any potential synergistic effects. Previous experiments have shown that kit ligand (KL), basic fibroblast growth factor (bFGF) and leukemia inhibitory factor (LIF) promote the primordial to primary follicle transition. Insulin was shown to have an additive effect with KL and LIF, but not bFGF. The fact that insulin can influence the primordial to primary follicle transition at low concentrations (i.e. 5 ng/ml) and that IGF-1 has no effect suggests that insulin is acting at the insulin receptor, not the IGF-1 receptor. The observation that insulin has an additive effect with KL and LIF, but not bFGF, suggests the insulin's site of action is likely the oocyte. In summary, observations suggest that insulin acts as an endocrine type factor to help coordinate primordial to primary follicle transition at the level of the oocyte. The significance of the observations in relation to diabetes and female infertility is discussed.