Search

Evolution in similar environments often leads to convergence of behavioral and anatomical traits. A classic example of convergent trait evolution is the reduced traits that characterize many cave animals: reduction or loss of pigmentation and eyes. While these traits have evolved many times, relatively little is known about whether these traits repeatedly evolve through the same or different molecular and developmental mechanisms. The small freshwater fish, Astyanax mexicanus, provides an opportunity to investigate the repeated evolution of cave traits. A. mexicanus exists as two forms, a sighted, surface-dwelling form and at least 29 populations of a blind, cave-dwelling form that initially develops eyes that subsequently degenerate. We compared eye morphology and the expression of eye regulatory genes in developing surface fish and two independently evolved cavefish populations, Pachón and Molino. We found that many of the previously described molecular and morphological alterations that occur during eye development in Pachón cavefish are also found in Molino cavefish. However, for many of these traits, the Molino cavefish have a less severe phenotype than Pachón cavefish. Further, cave-cave hybrid fish have larger eyes and lenses during early development compared with fish from either parental population, suggesting that some different changes underlie eye loss in these two populations. Together, these data support the hypothesis that these two cavefish populations evolved eye loss independently, yet through some of the same developmental and molecular mechanisms.

Loss-of-function mutations in the X-linked immunoglobulin superfamily, member 1 (IGSF1) gene result in central hypothyroidism, often associated with macroorchidism. Testicular enlargement in these patients might be caused by increases in follicle-stimulating hormone (FSH) levels, as IGSF1 has been proposed to function as an inhibin B receptor or as an inhibitor of activin type I receptor (ALK4) activity in pituitary gonadotrope cells. If true, loss of IGSF1 should lead to reduced inhibin B action or disinhibition of activin signaling, thereby increasing FSH synthesis. Here, we show that FSH levels and sperm counts are normal in male Igsf1 knockout mice, although testis size is mildly increased. Sperm parameters are also normal in men with IGSF1 deficiency, although their FSH levels may trend higher and their testes are enlarged. Inhibin B retains the ability to suppress FSH synthesis in pituitaries of Igsf1-knockout mice and IGSF1 does not interact with ALK4 or alter activin A/ALK4 stimulation of FSHβ (Fshb/FSHB) subunit transcription or expression. In light of these results, it is unlikely that macroorchidism in IGSF1 deficiency derives from alterations in spermatogenesis or inhibin/activin regulation of FSH.

Inhibins are gonadal hormones that suppress follicle-stimulating hormone (FSH) synthesis by pituitary gonadotrope cells. The structurally related activins stimulate FSH by signaling through complexes of type I and type II receptors. Two models of inhibin action were proposed in 2000. First, inhibins function as competitive receptor antagonists, binding activin type II receptors with high affinity in the presence of the TGF-β type III coreceptor, betaglycan. Second, immunoglobulin superfamily, member 1 (IGSF1, then called p120) was proposed to mediate inhibin B antagonism of activin signaling via its type I receptor. These ideas have been challenged over the past few years. Rather than playing a role in inhibin action, IGSF1 is involved in the central control of the thyroid gland. Betaglycan binds inhibin A and inhibin B with high affinity, but only functions as an obligate inhibin A coreceptor in murine gonadotropes. There is likely to be a distinct, but currently unidentified coreceptor for inhibin B.

Loss of function mutations in the X-linked immunoglobulin superfamily, member 1 (IGSF1) gene cause congenital central hypothyroidism, hypoprolactinemia, macroorchidism, and the dysregulation of growth hormone and pubertal development. IGSF1 is a type 1 transmembrane protein of unknown function that is highly expressed in the pituitary gland, choroid plexus, and developing liver. The mature form of the protein contains seven extracellular Ig loops, a single transmembrane domain, and a short intracellular carboxyl tail rich in serine and threonine residues. Although the function of IGSF1 is presently unknown, the topology of the protein suggests that it plays a role in intercellular communication. Two Igsf1 knockout mouse models exhibit reduced pituitary TRH receptor (Trhr1) expression and associated impairments in TRH-stimulated TSH secretion. How the loss of IGSF1 leads to reductions in Trhr1 levels is unresolved. We hypothesize that IGSF1 acts in concert with intracellular signaling molecules to regulate Trhr1 expression. To date, IGSF1 has been shown to interact with only two proteins, itself and the thyroid hormone transporter MCT8. However, MCT8 has low expression in the pituitary and IGSF1 does not alter MCT8-dependent thyroid hormone transport. Therefore, we implemented a new proximity labelling method, BioID, to characterize the intracellular IGSF1 interactome and ultimately determine IGSF1’s role in Trhr1 regulation. We expressed an IGSF1-BirA* fusion protein in heterologous cells and confirmed that it properly traffics to the plasma membrane. Moreover, the protein auto-biotinylates and labels other, currently unidentified proteins. IGSF1-BirA* maintains its ability to interact with MCT8, but does not interact with an intracellular signaling protein recently implicated in central hypothyroidism, insulin receptor substrate 4 (IRS4). We are stably expressing IGSF1-BirA* in heterologous and homologous cell lines, HEK293 and HepG2 (human hepatocellular carcinoma), respectively, for the BioID screen. We will purify biotinylated proteins and identify them using mass spectrometry. In follow-up analyses, we will focus on proteins that link IGSF1 to known signaling pathways.

Amyotrophic lateral sclerosis (ALS) is characterized by progressive muscle atrophy resulting from the deterioration of motor neurons in the central nervous system (CNS). Recent genome-wide association studies have revealed several genes linked to ALS, further demonstrating the complexity of the disease. The zebrafish (Danio rerio) is an attractive model organism to study the function of the rapidly expanding number of ALS-associated genes, in part, due to the development of genome editing techniques that have facilitated specific gene targeting. Before investing in the manipulation and phenotypic examination of these genes, however, it is important to ascertain the localization of expression in this organism. We performed an expression analysis of 29 total ALS-linked genes in the developing zebrafish, specifically focusing on those genes that displayed robust and reproducible expression at multiple different timepoints. First, we classified a subset of the most robustly expressed genes into three distinct groups: head-only expression, head and weak trunk expression, and head and robust trunk expression. Then, we defined the characteristic pattern of each gene at 2, 3, and 4 days post fertilization. This analysis will facilitate improved mutant phenotype assessment in zebrafish by focusing researchers on the areas of expression.

Immunoglobulin superfamily, member 1 (IGSF1) is a transmembrane glycoprotein highly expressed in the mammalian pituitary gland. Shortly after its discovery in 1998, the protein was proposed to function as a coreceptor for inhibins (and was even temporarily renamed inhibin binding protein). However, subsequent investigations, both in vitro and in vivo, failed to support a role for IGSF1 in inhibin action. Research on IGSF1 nearly ground to a halt until 2011, when next-generation sequencing identified mutations in the X-linked IGSF1 gene in boys and men with congenital central hypothyroidism. IGSF1 was localized to thyrotrope cells, implicating the protein in pituitary control of the thyroid. Investigations in two Igsf1 knockout mouse models converged to show that IGSF1 deficiency leads to reduced expression of the receptor for thyrotropin-releasing hormone (TRH) and impaired TRH stimulation of thyrotropin secretion, providing a candidate mechanism for the central hypothyroidism observed in patients. Nevertheless, the normal functions of IGSF1 in thyrotropes and other cells remain unresolved. Moreover, IGSF1 mutations are also commonly associated with other clinical phenotypes, including prolactin and growth hormone dysregulation, and macroorchidism. How the loss of IGSF1 produces these characteristics is unknown. Although early studies of IGSF1 ran into roadblocks and blind alleys, armed with the results of detailed clinical investigations, powerful mouse models, and new reagents, the field is now poised to discover IGSF1’s function in endocrine tissues, including the pituitary and testes., This review discusses how loss of function mutations in the IGSF1 gene may cause central hypothyroidism and identifies areas of current and future investigation.

The corpus luteum (CL) develops from the remnants of the ovulatory follicle and produces progesterone, required for maintenance of pregnancy in mammals. The differentiation of granulosal and thecal cells into luteal cells is accompanied by hypertrophy and hyperplasia of cells. As the CL matures, growth ceases and in ruminants, the tissue acquires the ability to undergo regression in response to prostaglandin F2alpha. The regulators of this transition are poorly understood. MicroRNA, which are posttranscriptional regulators of tissue development and function, are expressed in the CL. However, the pattern of their expression and their function during the transition from developing to functional CL is not known. The objectives of this study were to profile the expression of miRNA in developing versus mature bovine CL and determine effects of miRNA on bovine luteal cell survival and function. Knockdown of Drosha in midcycle (MC) luteal cells decreased progesterone and increased luteal cell apoptosis in the presence or absence of proinflammatory cytokines. Microarray analysis demonstrated that a greater number of miRNA were expressed in MC compared to D4 CL. Ingenuity pathway analysis (IPA) predicted that D4-specific miRNA regulate pathways related to carbohydrate metabolism, while MC-specific miRNA regulate pathways related to cell cycle and apoptosis signaling. Both predictions are consistent with a switch in the CL from a growing phase to a maintenance phase. One of the MC specific miRNA, miR-34a, was selected for further analysis. Increased concentrations of miR-34a in MC luteal cells resulted in decreased luteal cell proliferation, increased progesterone production, and inhibition of Notch1 and YY1 translation, but had no effect on luteal cell apoptosis. In conclusion, these data support a role for miRNA in general, and miR-34a in particular, in luteal formation and function.

The corpus luteum (CL) develops from the remnants of the ovulatory follicle and produces progesterone, required for maintenance of pregnancy in mammals. The differentiation of granulosal and thecal cells into luteal cells is accompanied by hypertrophy and hyperplasia of cells. As the CL matures, growth ceases and in ruminants, the tissue acquires the ability to undergo regression in response to prostaglandin F2alpha. The regulators of this transition are poorly understood. MicroRNA, which are posttranscriptional regulators of tissue development and function, are expressed in the CL. However, the pattern of their expression and their function during the transition from developing to functional CL is not known. The objectives of this study were to profile the expression of miRNA in developing versus mature bovine CL and determine effects of miRNA on bovine luteal cell survival and function. Knockdown of Drosha in midcycle (MC) luteal cells decreased progesterone and increased luteal cell apoptosis in the presence or absence of proinflammatory cytokines. Microarray analysis demonstrated that a greater number of miRNA were expressed in MC compared to D4 CL. Ingenuity pathway analysis (IPA) predicted that D4-specific miRNA regulate pathways related to carbohydrate metabolism, while MC-specific miRNA regulate pathways related to cell cycle and apoptosis signaling. Both predictions are consistent with a switch in the CL from a growing phase to a maintenance phase. One of the MC specific miRNA, miR-34a, was selected for further analysis. Increased concentrations of miR-34a in MC luteal cells resulted in decreased luteal cell proliferation, increased progesterone production, and inhibition of Notch1 and YY1 translation, but had no effect on luteal cell apoptosis. In conclusion, these data support a role for miRNA in general, and miR-34a in particular, in luteal formation and function.

Curetting the uterus for endometritis, subinvolution, retained products of conception, etc., has come to be a very common operation. It is deservedly recognized as a valuable procedure in these conditions, and accomplishes speedily what local treatment or the exhibition of medicines can not. It needs no argument to prove that unless curetting is thoroughly done, and the material scraped off is removed from the cavity of the uterus, the operation is apt to do more harm than good. I think the experience of the majority of physicians will bear me out in the statement that there is a large element of uncertainty in performing curettage with the ordinary spoon curette. We are never sure, in using this instrument, that we have not neglected to reach some portion of the mucous surface, or that some shreds of tissue have not been left behind to cause trouble. The instrument shown in the