SUMMARY Self-fertile hermaphrodites have evolved independently several times in the genus Caenorhabditis [1, 2]. These XX hermaphrodites make smaller sperm than males [3, 4], which they use to fertilize their own oocytes. Since larger sperm outcompete smaller sperm in nematodes [3–5], it had been assumed that this dimorphism evolved in response to sperm competition. However, we show that it was instead caused by a developmental bias. When we transformed females of the species C. remanei into hermaphrodites [6], their sperm were significantly smaller than those of males. Because this species never makes hermaphrodites in the wild, this dimorphism cannot be due to selection. Instead, analyses of the related nematode C. elegans suggest that this dimorphism might reflect the development of sperm within the distinct physiological environment of the hermaphrodite gonad. These results reveal a new mechanism for some types of developmental bias — the effects of a novel physical location alter the development of ectopic cells in predictable ways.

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The environment within the Endoplasmic Reticulum (ER) influences Insulin biogenesis. In particular, ER stress may contribute to the development of Type 2 Diabetes (T2D) and Cystic Fibrosis Related Diabetes (CFRD), where evidence of impaired Insulin processing, including elevated secreted Proinsulin/Insulin ratios, are observed. Our group has established the role of a novel ER chaperone ERp29 (ER protein of 29 kDa) in the biogenesis of the Epithelial Sodium Channel, ENaC. The biogenesis of Insulin and ENaC share may key features, including their potential association with COP II machinery, their cleavage into a more active form in the Golgi or later compartments, and their ability to bypass such cleavage and remain in a less active form. Given these similarities we hypothesized that ERp29 is a critical factor in promoting the efficient conversion of Proinsulin to Insulin. Here, we confirmed that Proinsulin associates with the COP II vesicle cargo recognition component, Sec24D. When Sec24D expression was decreased, we observed a corresponding decrease in whole cell Proinsulin levels. In addition, we found that Sec24D associates with ERp29 in co-precipitation experiments and that ERp29 associates with Proinsulin in co-precipitation experiments. When ERp29 was overexpressed, a corresponding increase in whole cell Proinsulin levels was observed, while depletion of ERp29 decreased whole cell Proinsulin levels. Together, these data suggest a potential role for ERp29 in regulating Insulin biosynthesis, perhaps in promoting the exit of Proinsulin from the ER via Sec24D/COPII vesicles.

The normal function of any organism, its organizational complexity notwithstanding, depends on the interaction of its proteins with their targets. Thus, analysis of target site interaction is an essential part of all biology. At the protein level, such analyses are critical to both mechanistic knowledge and potential clinical applications such as drug discovery. Approaches to map amino acid residues involved in target site interaction typically are experimental or are based on three-dimensional structures obtained through crystallography. Here we test a novel approach that combines phylogenetic analyses with mining of experimental data using neuronal calcium sensor proteins. The proteins fall into three groups based on sequence comparison. One interaction was taken up for analysis from each group. Using the sequence divergence to evaluate the role of amino acids identified experimentally to form the interface with the target, we demonstrate that it is possible to predict residues that are likely to contribute to the specificity of the interaction and, therefore, the functional divergence. Thus, evolutionary analyses of proteins provide an important addition in approaches to generate refined maps of target site interactions in proteins. This approach is especially useful in delineating the functional divergence in a family of closely related proteins.