Sex-specific markers undetected in green sunfish Lepomis cyanellus using restriction-site associated DNA sequencing.

We used restriction-site associated DNA sequencing for SNP discovery and genotyping of known-sex green sunfish Lepomis cyanellus DNA samples to search for sex-diagnostic single nucleotide polymorphisms (SNPs) and restriction-site associated sequences present in one sex and absent in the other. The bioinformatic analyses discovered candidate SNPs and sex-specific restriction-site associated sequences that fit patterns of male or female heterogametic sex determination systems. However, when primers were developed and tested, no candidates reliably identified phenotypic sex. The top performing SNP candidate (ZW_218) correlated with phenotypic sex 63.0% of the time and the presence-absence loci universally amplified in both sexes. We recommend further investigations that interrogate a larger fraction of the L. cyanellus genome. Additionally, studies on the effect of temperature and rearing density on sex determination, as well as breeding of sex-reversed individuals, could provide more insights into the sex determination system of L. cyanellus.

The Gill-Oxygen Limitation Theory and size at maturity/maximum size relationships for salmonid populations occupying flowing waters.

The slowing of growth as fish age has long been believed to be related to energy expenditure for maturation, and this rationalization has been used to explain why, across nearly all fish species, the relationship between size at first maturity (Lm ) and maximum (Lmax ) or asymptotic length (L∞ ) is relatively constant. In contrast, the Gill-Oxygen Limitation Theory (GOLT) postulates that (a) fish growth slows because as they grow, their two-dimensional ability to extract oxygen from the water diminishes relative to their three-dimensional weight gain, and (b) they can only invest energy for maturation if oxygen supply at their size at first maturity (Qm ) exceeds that needed for maintenance metabolism (Q∞ ). It has been reported previously across dozens of marine fish species that the relationship between Qm and Q∞ is linear and, further, it can be mathematically converted to Lm vs. L∞ by raising both terms to the power of D (the gill surface factor), resulting in a slope of 1.36. If the GOLT is universal, a similar slope should exist for Lm D vs. L∞ D relationships for freshwater species across multiple individual populations that reside in disparate habitats, although to our knowledge this has never been evaluated. For analysis, we used existing data from previous studies conducted on 51 stream-dwelling populations of redband trout Oncorhynchus mykiss gairdneri, Yellowstone cutthroat trout O. clarkii bouvieri and mountain whitefish Prosopium williamsoni. The resulting Lm D vs. L∞ D slopes combining all data points (1.35) or for all species considered separately (range = 1.29-1.40) were indeed equivalent to the slope originally produced for the marine species from which the GOLT-derived relationship was first reported. We briefly discuss select papers both supporting and resisting various aspects of the GOLT, note that it could potentially explain shrinking sizes of marine fish, and call for more concerted research efforts combining laboratory and field expertise in fish growth research.

Human-Induced Pluripotent Stem Cell (iPSC)-Derived GABAergic Neuron Differentiation in Bipolar Disorder.

Bipolar disorder (BP) is a recurring psychiatric condition characterized by alternating episodes of low energy (depressions) followed by manias (high energy). Cortical network activity produced by GABAergic interneurons may be critical in maintaining the balance in excitatory/inhibitory activity in the brain during development. Initially, GABAergic signaling is excitatory; with maturation, these cells undergo a functional switch that converts GABAA channels from depolarizing (excitatory) to hyperpolarizing (inhibitory), which is controlled by the intracellular concentration of two chloride transporters. The earliest, NKCC1, promotes chloride entry into the cell and depolarization, while the second (KCC2) stimulates movement of chloride from the neuron, hyperpolarizing it. Perturbations in the timing or expression of NKCC1/KCC2 may affect essential morphogenetic events including cell proliferation, migration, synaptogenesis and plasticity, and thereby the structure and function of the cortex. We derived induced pluripotent stem cells (iPSC) from BP patients and undiagnosed control (C) individuals, then modified a differentiation protocol to form GABAergic interneurons, harvesting cells at sequential stages of differentiation. qRT-PCR and RNA sequencing indicated that after six weeks of differentiation, controls transiently expressed high levels of NKCC1. Using multi-electrode array (MEA) analysis, we observed that BP neurons exhibit increased firing, network bursting and decreased synchrony compared to C. Understanding GABA signaling in differentiation may identify novel approaches and new targets for treatment of neuropsychiatric disorders such as BP.

Modification of HDL by reactive aldehydes alters select cardioprotective functions of HDL in macrophages.

While increased levels of high-density lipoprotein (HDL)-cholesterol correlate with protection against cardiovascular disease, recent findings demonstrate that HDL function, rather than HDL-cholesterol levels, may be a better indicator of cardiovascular risk. One mechanism by which HDL function can be compromised is through modification by reactive aldehydes such as acrolein (Acro), 4-hydroxynonenal, and malondialdehyde (MDA). In this study, we tested the hypothesis that modification of HDL with reactive aldehydes would impair HDL's athero-protective functions in macrophages. Compared to native HDL, Acro- and MDA-modified HDL have impaired abilities to promote migration of primary peritoneal macrophages isolated from C57BL6/J mice. Incubation of macrophages with MDA-HDL also led to an increased ability to generate reactive oxygen species. Our studies revealed that the changes in HDL function following aldehyde modification are likely not through activation of canonical nuclear factor-kappa B signaling pathways. Consistent with this finding, treatment of either noncholesterol-loaded macrophages or foam cells with modified forms of HDL does not lead to significant changes in expression levels of inflammatory markers. Importantly, our data also demonstrate that changes in HDL function are dependent on the type of modification present on the HDL particle. Our findings suggest that modification of HDL with reactive aldehydes can impair some, but not all, of HDL's athero-protective functions in macrophages.