We examined the effects of 3 diets differing in their relative levels of sugar and protein on development and metabolic pools (protein, TG, and glycogen) among sets of isofemale lines of 2 ecologically distinct Drosophila species, D. melanogaster and D. mojavensis. Our high protein:sugar ratio diet contained 7.1% protein and 17.9% carbohydrate, the EPS diet was 4.3% protein and 21.2% carbohydrate, and the LPS was only 2.5% protein and 24.6% carbohydrate. Larvae of D. melanogaster, a generalist fruit breeder, were able to survive on all 3 diets, although all 3 metabolic pools responded with significant diet and diet × line interactions. Development was delayed by the diet with the most sugar relative to protein. The other species, D. mojavensis, a cactus breeder ecologically unaccustomed to encountering simple sugars, completely failed to survive when fed the diet with the highest sugar and showed very poor survival even with the diet with equal parts of protein and sugar. Furthermore, the D. mojavensis adult metabolic pools of protein, TG, and glycogen significantly differed from those of D. melanogaster adults fed the identical diet. Thus, considerable within- and between-species differences exist in how diets are metabolized. Given that the genomes of both of these Drosophila species have been sequenced, these differences and their genetic underpinnings hold promise for understanding human responses to nutrition and for developing strategies for dealing with metabolic disease.

BackgroundDescribing the patterns of gene expression during embryonic development has broadened our understanding of the processes and patterns that define morphogenesis. Yet gene expression patterns have not been described throughout vertebrate embryogenesis. This study presents statistical analyses of gene expression during all 40 developmental stages in the teleost Fundulus heteroclitus using four biological replicates per stage.ResultsPatterns of gene expression for 7,000 genes appear to be important as they recapitulate developmental timing. Among the 45% of genes with significant expression differences between pairs of temporally adjacent stages, significant differences in gene expression vary from as few as five to more than 660. Five adjacent stages have disproportionately more significant changes in gene expression (> 200 genes) relative to other stages: four to eight and eight to sixteen cell stages, onset of circulation, pre and post-hatch, and during complete yolk absorption. The fewest differences among adjacent stages occur during gastrulation. Yet, at stage 16, (pre-mid-gastrulation) the largest number of genes has peak expression. This stage has an over representation of genes in oxidative respiration and protein expression (ribosomes, translational genes and proteases). Unexpectedly, among all ribosomal genes, both strong positive and negative correlations occur. Similar correlated patterns of expression occur among all significant genes.ConclusionsThese data provide statistical support for the temporal dynamics of developmental gene expression during all stages of vertebrate development.

Changes in gene expression, coupled with biochemical, physiological, and behavioral alterations, play a critical role in adaptation to environmental stress. Our goal was to explore ways natural populations may have adapted to local, polluted environments. We took advantage of natural populations of Fundulus heteroclitus, one of the few studied fish species in North America that has established resistant populations in highly contaminated urban estuaries. We analyzed morphology, physiology, and gene expression of developing F. heteroclitus embryos during late organogenesis (stage 31); these embryos were from both resistant and sensitive populations and were raised in a common, unpolluted environment. While cardiac heart rates show significant differences between embryos of parents from clean and heavily contaminated Superfund sites, time-to-stage, embryo morphology, and gene expression profile analyses do not differ significantly between untreated embryos from resistant and sensitive populations. Further evaluation that includes tissue-specific approaches in gene expression analysis and larger sample sizes may be necessary to highlight important phenotypes associated with mechanisms of sensitivity and resistance among natural F. heteroclitus embryo populations. Alternatively, population differences may be masked by developmental canalization, and biologically important differences between sensitive and resistant embryos may only manifest with exposure (e.g., be dependent on gene by environment interactions).

BackgroundAdaptations to a new environment, such as a polluted one, often involve large modifications of the existing phenotypes. Changes in gene expression and regulation during critical developmental stages may explain these phenotypic changes. Embryos from a population of the teleost fish, Fundulus heteroclitus, inhabiting a clean estuary do not survive when exposed to sediment extract from a site highly contaminated with polycyclic aromatic hydrocarbons (PAHs) while embryos derived from a population inhabiting a PAH polluted estuary are remarkably resistant to the polluted sediment extract. We exposed embryos from these two populations to surrogate model PAHs and analyzed changes in gene expression, morphology, and cardiac physiology in order to better understand sensitivity and adaptive resistance mechanisms mediating PAH exposure during development.ResultsThe synergistic effects of two model PAHs, an aryl hydrocarbon receptor (AHR) agonist (β-naphthoflavone) and a cytochrome P4501A (CYP1A) inhibitor (α-naphthoflavone), caused significant developmental delays, impaired cardiac function, severe morphological alterations and failure to hatch, leading to the deaths of reference embryos; resistant embryos were mostly unaffected. Unexpectedly, patterns of gene expression among normal and moderately deformed embryos were similar, and only severely deformed embryos showed a contrasting pattern of gene expression. Given the drastic morphological differences between reference and resistant embryos, a surprisingly low percentage of genes, 2.24% of 6,754 analyzed, show statistically significant differences in transcript levels during late organogenesis between the two embryo populations.ConclusionsOur study demonstrates important contrasts in responses between reference and resistant natural embryo populations to synergistic effects of surrogate model PAHs that may be important in adaptive mechanisms mediating PAH effects during fish embryo development. These results suggest that statistically significant changes in gene expression of relatively few genes contribute to the phenotypic changes and large morphological differences exhibited by reference and resistant populations upon exposure to PAH pollutants. By correlating cardiac physiology and morphology with changes in gene expression patterns of reference and resistant embryos, we provide additional evidence for acquired resistance among embryos whose parents live at heavily contaminated sites.

Transcriptomics and population genomics are two complementary genomic approaches that can be used to gain insight into pollutant effects in natural populations. Transcriptomics identify altered gene expression pathways while population genomics approaches more directly target the causative genomic polymorphisms. Neither approach is restricted to a pre-determined set of genes or loci. Instead, both approaches allow a broad overview of genomic processes. Transcriptomics and population genomic approaches have been used to explore genomic responses in populations of fish from polluted environments and have identified sets of candidate genes and loci that appear biologically important in response to pollution. Often differences in gene expression or loci between polluted and reference populations are not conserved among polluted populations suggesting a biological complexity that we do not yet fully understand. As genomic approaches become less expensive with the advent of new sequencing and genotyping technologies, they will be more widely used in complimentary studies. However, while these genomic approaches are immensely powerful for identifying candidate gene and loci, the challenge of determining biological mechanisms that link genotypes and phenotypes remains. Keywords Fundulus heteroclitus; Genomics; Natural populations; Pollution Genomics with natural populationsThe power of genomic tools is the ability to simultaneously query large portions of the genome of an organism. These tools are just beginning to be harnessed for studies of aquatic toxicology in natural populations. The advantage of genomic approaches used in aquatic toxicology studies of natural populations is that an a priori choice of biomarkers of adverse effect is not necessary. This can be particularly important when organisms are exposed to mixtures of chemicals, as is often the case in environmental studies. Since the biological targets of pollutants often are not fully known, the global view gained with genomic approaches can be particularly valuable.Two complementary genomic approaches that are becoming easier and cheaper to implement with non-model, natural populations are microarrays and population genomics.

Polycyclic aromatic hydrocarbons (PAHs) are among the most widespread natural and anthropogenic pollutants, and some PAHs are proven developmental toxicants. We chemically characterized clean and heavily polluted sites and exposed fish embryos to PAH polluted sediment extracts during four critical developmental stages. Embryos were collected from Fundulus heteroclitus populations inhabiting the clean and heavily polluted Superfund estuary. Embryos of parents from the clean sites are sensitive to PAH pollutants while those of parents from the heavily polluted site are resistant. Chemical analysis of embryos suggests PAH accumulation and pollution-induced toxicity among sensitive embryos during development that ultimately kills all sensitive embryos before hatching, while remarkably, the resistant embryos develop normally. The adverse effects on sensitive embryos are manifested as developmental delays, reduced heart rates, and severe heart, liver, and kidney morphological abnormalities. Gene expression analysis of early somitogenesis, heartbeat initiation, late organogenesis, and pre-hatching developmental stages reveals genes whose expression significantly differs between sensitive and resistant embryo populations and helps to explain mechanisms of sensitivity and resistance to polluted environments during vertebrate animal development.

Attention-deficit/hyperactivity disorder (ADHD), the most diagnosed emerging neurodevelopmental disorder in children, is a growing health crisis in the United States. Due to the potential increase in ADHD severity during and post the COVID-19 pandemic, we analyzed recent national and two state-specific ADHD data distribution among U.S. children and adolescents by investigating a broad range of socioeconomic status (SES) factors. Child and adolescent ADHD diagnosis and treatment data were parent-reported via National Survey of Children’s Health (NSCH). The nationwide childhood prevalence of ADHD is 8.7%, and 62.1% of diagnosed children are taking medication. Louisiana (15.7%) has the highest percentage of children diagnosed with ADHD and California (5.6%) has the lowest, followed by Nevada (5.9%). Multiple correspondence analysis (MCA, n = 51,939) examining 30 factors highlights four areas of interest at the national and state level: race/ethnicity, financial status, family structure, and neighborhood characteristics. Positive correlations between ADHD diagnosis and unsafe school, unsafe neighborhood, and economic hardship are evident nationally and statewide, while the association between a lack of ADHD diagnosis and higher urban neighborhood amenities are evident nationally, but not in two opposing outlier states—Louisiana or Nevada. National and state-specific hierarchical analyses demonstrate significant correlations between the various SES factors and ADHD outcomes. Since the national analysis does not account for the demographic heterogeneity within regions or individual states, the U.S. should rely on comprehensive, county-specific, near real-time data reporting to effectively model and mitigate the ADHD epidemic and similar national health crises.

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