Neil M. Wolfman

Chronic mucocutaneous candidiasis disease (CMCD) is characterized by recurrent or persistent infections of the skin, nails, and oral and genital mucosae caused by Candida albicans and, to a lesser extent, Staphylococcus aureus, in patients with no other infectious or autoimmune manifestations. We report two genetic etiologies of CMCD: autosomal recessive deficiency in the cytokine receptor, interleukin-17 receptor A (IL-17RA), and autosomal dominant deficiency of the cytokine interleukin-17F (IL-17F). IL-17RA deficiency is complete, abolishing cellular responses to IL-17A and IL-17F homo- and heterodimers. By contrast, IL-17F deficiency is partial, with mutant IL-17F-containing homo- and heterodimers displaying impaired, but not abolished, activity. These experiments of nature indicate that human IL-17A and IL-17F are essential for mucocutaneous immunity against C. albicans, but otherwise largely redundant.

Mice and cattle with genetic deficiencies in myostatin exhibit dramatic increases in skeletal muscle mass, suggesting that myostatin normally suppresses muscle growth. Whether this increased muscling results from prenatal or postnatal lack of myostatin activity is unknown. Here we show that myostatin circulates in the blood of adult mice in a latent form that can be activated by acid treatment. Systemic overexpression of myostatin in adult mice was found to induce profound muscle and fat loss analogous to that seen in human cachexia syndromes. These data indicate that myostatin acts systemically in adult animals and may be a useful pharmacologic target in clinical settings such as cachexia, where muscle growth is desired.

Although the transforming growth factor-beta (TGF-beta) superfamily is the largest family of secreted growth factors, surprisingly few downstream target genes in their signaling pathways have been identified. Likewise, the identities of oocyte-derived secreted factors, which regulate important oocyte-somatic cell interactions, remain largely unknown. For example, oocytes are known to secrete paracrine growth factor(s) which are necessary for cumulus expansion, induction of hyaluronic acid synthesis, and suppression of LH receptor (LHR) mRNA synthesis. Our previous studies demonstrated that absence of the TGF-beta family member, growth differentiation factor-9 (GDF-9), blocks ovarian folliculogenesis at the primary follicle stage leading to infertility. In the present study, we demonstrate that mouse GDF-9 protein is expressed in all oocytes beginning at the type 3a follicle stage including antral follicles. To explore the biological functions of GDF-9 in the later stages of folliculogenesis and cumulus expansion, we produced mature, glycosylated, recombinant mouse GDF-9 using a Chinese hamster ovary cell expression system. A granulosa cell culture system was established to determine the role of GDF-9 in the regulation of several key ovarian gene products using semiquantitative RT-PCR. We find that recombinant GDF-9 induces hyaluronan synthase 2 (HAS2), cyclooxygenase 2 (COX-2), and steroidogenic acute regulator protein (StAR) mRNA synthesis but suppresses urokinase plasminogen activator (uPA) and LHR mRNA synthesis. Consistent with the induction of StAR mRNA by GDF-9, recombinant GDF-9 increases granulosa cell progesterone synthesis in the absence of FSH. Since induction of HAS2 and suppression of the protease uPA in cumulus cells are key events in the production of the hyaluronic acid-rich extracellular matrix which is produced during cumulus expansion, we determined whether GDF-9 could mimic this process. Using oocytectomized cumulus cell-oocyte complexes, we show that recombinant GDF-9 induces cumulus expansion in vitro. These studies demonstrate that GDF-9 can bind to receptors on granulosa cells to regulate the expression of a number of gene products. Thus, in addition to playing a critical function as a growth and differentiation factor during early folliculogenesis, GDF-9 functions as an oocyte-secreted paracrine factor to regulate several key granulosa cell enzymes involved in cumulus expansion and maintenance of an optimal oocyte microenvironment, processes which are essential for normal ovulation, fertilization, and female reproduction.

Little is known about the regulatory signals involved in tendon and ligament formation, and this lack of understanding has hindered attempts to develop biologically based therapies for tendon and ligament repair. Here we report that growth and differentiation factors (GDFs) 5, 6, and 7, members of the TGF-beta gene superfamily that are most related to the bone morphogenetic proteins, induce neotendon/ligament formation when implanted at ectopic sites in vivo. Analysis of tissue induced by GDF-5, 6, or 7, containing implants by currently available morphological and molecular criteria used to characterize tendon and ligament, adds further evidence to the idea that these GDFs act as signaling molecules during embryonic tendon/ligament formation. In addition, comparative in situ localizations of the GDF-5, 6, and 7 mRNAs suggest that these molecules are important regulatory components of synovial joint morphogenesis.

Myostatin is a secreted protein that normally functions as a negative regulator of muscle growth. Agents capable of blocking the myostatin signaling pathway could have important applications for treating human muscle degenerative diseases as well as for enhancing livestock production. Here we describe a potent myostatin inhibitor, a soluble form of the activin type IIB receptor (ACVR2B), which can cause dramatic increases in muscle mass (up to 60% in 2 weeks) when injected into wild-type mice. Furthermore, we show that the effect of the soluble receptor is attenuated but not eliminated in Mstn(-/-) mice, suggesting that at least one other ligand in addition to myostatin normally functions to limit muscle growth. Finally, we provide genetic evidence that these ligands signal through both activin type II receptors, ACVR2 and ACVR2B, to regulate muscle growth in vivo.