No abstract

The gap junction protein Connexin 43 (Cx43) contributes to cell fate decisions that determine the location of fin ray joints during regeneration. Here, we provide insights into how Cx43, expressed medially, influences changes in gene expression in lateral skeletal precursor cells. Using the Gap27 peptide inhibitor specific to Cx43, we show that Cx43-gap junctional intercellular communication (GJIC) influences Cx43-dependent skeletal phenotypes, including segment length. We also demonstrate that Cx43-GJIC influences the expression of the Smp/β-catenin pathway in the lateral skeletal precursor cells, and does not influence the Sema3d pathway. Moreover, we show that the cx43 lh10 allele, which has increased Cx43 protein levels, exhibits increased regenerate length and segment length. These phenotypes are rescued by Gap27, suggesting that increased Cx43 is responsible for the observed Cx43 phenotypes. Finally, our findings suggest that inhibition of Cx43 hemichannel activity does not influence Cx43-dependent skeletal phenotypes. These data provide evidence that Cx43-GJIC is responsible for regulating cell fate decisions associated with appropriate joint formation in the regenerating fin.

Members of the disintegrin metalloproteinase (ADAM) family have important functions in regulating cell-cell and cell-matrix interactions as well as cell signaling. There are two major types of ADAMs: the somatic ADAMs (sADAMs) that have a significant presence in somatic tissues, and the testicular ADAMs (tADAMs) that are expressed predominantly in the testis. Genes encoding tADAMs can be further divided into two groups: group I (intronless) and group II (intron-containing). To date, tAdams have only been reported in placental mammals, and their evolutionary origin and relationship to sAdams remain largely unknown. Using phylogenetic and syntenic tools, we analyzed the Adam genes in various vertebrates ranging from fishes to placental mammals. Our analyses reveal duplication and loss of some sAdams in certain vertebrate species. In particular, there exists an Adam9-like gene in non-mammalian vertebrates but not mammals. We also identified putative group I and group II tAdams in all amniote species that have been examined. These tAdam homologues are more closely related to Adams 9 and 9-like than to other sAdams. In all amniote species examined, group II tAdams lie in close vicinity to Adam9 and hence likely arose from tandem duplication, whereas group I tAdams likely originated through retroposition because of their lack of introns. Clusters of multiple group I tAdams are also common, suggesting tandem duplication after retroposition. Therefore, Adam9/9-like and some of the derived tAdam loci are likely preferred targets for tandem duplication and/or retroposition. Consistent with this hypothesis, we identified a young retroposed gene that duplicated recently from Adam9 in the opossum. As a result of gene duplication, some tAdams were pseudogenized in certain species, whereas others acquired new expression patterns and functions. The rapid duplication of Adam genes has a major contribution to the diversity of ADAMs in various vertebrate species.

The correct positioning of joints in the vertebrate skeleton is not well understood. Mutations in connexin43 (cx43) cause the short segment phenotype of the zebrafish short fin (sof b123) mutant. We have shown that Cx43 suppresses evx1 expression, a transcription factor required for joint formation. Here, we provide novel insights into how Cx43 influences evx1 transcription. First, we find that Simplet (Smp) knockdown recapitulates the sof b123 phenotypes of reduced regenerate length and reduced segment length, and we find evidence for synergy between cx43 and smp. Moreover, knockdown of Smp increases the evx1 expression, similar to cx43 knockdown. Previous studies have shown that Smp is required for the nuclear localization of β-catenin. Indeed, β-catenin activity is required for segment length, and is reduced in both sof b123 mutants and following Smp knockdown in regenerating fins. We further show that blocking canonical Wnt signaling results in a synergistic reduction in segment length in sof b123/+ heterozygotes. Together, our findings suggest that both Smp and β-catenin function in a common molecular pathway with cx43 to influence both evx1 expression and joint location.

Types of Co-existing Chronic Physical Conditions and Newly-diagnosed Depression, its Treatment and Economic Outcomes among Medicaid Beneficiaries with Type 2 DiabetesRituparna Bhattacharya, B. Pharm., M.S.Diabetes is a widely prevalent metabolic condition. Adults with type 2 diabetes mellitus (T2DM) also have many coexisting chronic physical conditions. Coexisting chronic physical conditions among individuals with T2DM may be concordant (conditions that overlap with T2DM in their pathogenesis and management plans such as cardiovascular diseases) or discordant (conditions with unrelated pathogenesis or management plans such as musculoskeletal disorders) or dominant (conditions whose severity eclipses all other illness management plans such as metastatic cancer). There is documented evidence on the negative consequences of depression in adults with T2DM. However, there is only limited knowledge on how the types of coexisting chronic physical conditions (defined as concordant, discordant or dominant conditions) influence the risk for developing depression, subsequent depression treatment patterns and economic consequences of depression treatment, among adults with T2DM. Therefore the aims of this dissertation were to examine (1) the association of risk of newly-diagnosed depression with types of coexisting chronic physical conditions among adults with T2DM (2) the association between types of coexisting chronic physical conditions and depression treatment among adults with T2DM and newly-diagnosed depression was analyzed and (3) whether the relationship between depression treatment and total and T2DM-related healthcare care expenditures vary by types of coexisting chronic physical conditions among non-elderly adult Medicaid beneficiaries with T2DM and newly-diagnosed depression. A retrospective longitudinal cohort study design was used. Patient-level data were obtained from multi-year, multi-state Medicaid claims. Non-elderly (ages 18-64), fee-for-service Medicaid beneficiaries with T2DM who were depression free were followed for a period of 12 months to identify newly-diagnosed depression. The final study population consisted of 59,857 Medicaid beneficiaries of whom N=5,974 had newly diagnosed depression. After controlling for other risk factors, those with dominant conditions were at 17% higher risk (p=0.0006) and those with both concordant and discordant conditions were found to be at 30% higher risk (p<.0001) to develop newly-diagnosed depression as compared to those with concordant conditions only. Individuals with dominant conditions (p<0.05) were less likely to receive depression treatment with only antidepressants compared to those with discordant conditions only. Individuals with dominant conditions were more likely to receive depression treatment with only psychotherapy (p<.01) as compared to those with discordant conditions only. No statistically significant associations were observed between types of coexisting chronic physical conditions and receipt of adequate depression treatment. As compared to no de...