Occurrence of dactylogyrid and gyrodactylid Monogenea on common carp, Cyprinus carpio, in the Southern Caspian Sea Basin.

In this study, we genetically characterised Monogenea found on common carp in Iran. In total, 5603 parasites were recovered from 112 fish. The parasites were first identified morphologically as Dactylogyrus extensus, D. anchoratus, D. vastator, D. minutus, D. achmerowi and Gyrodactylus sprostonae. Representative samples were then subjected to sequencing. This is one of the first studies which has provided both morphological and sequence data for Dactylogyrus spp. and G. sprostonae. Our findings provide a foundation for future research into the genetic make-up of these economically significant parasites and the establishment of effective strategies for their control and prevention in aquaculture systems.

Genetic variation in brain-derived neurotrophic factor and human fear conditioning.

Brain-derived neurotrophic factor (BDNF) has been implicated in hippocampal-dependent learning processes, and carriers of the Met allele of the Val66Met BDNF genotype are characterized by reduced hippocampal structure and function. Recent nonhuman animal work suggests that BDNF is also crucial for amygdala-dependent associative learning. The present study sought to examine fear conditioning as a function of the BDNF polymorphism. Fifty-seven participants were genotyped for the BDNF polymorphism and took part in a differential-conditioning paradigm. Participants were shocked following a particular conditioned stimulus (CS+) and were also presented with stimuli that ranged in perceptual similarity to the CS+ (20, 40 or 60% smaller or larger than the CS+). The eye blink component of the startle response was measured to quantify fear conditioning; post-task shock likelihood ratings for each stimulus were also obtained. All participants reported that shock likelihood varied with perceptual similarity to the CS+ and showed potentiated startle in response to CS +/- 20% stimuli. However, only the Val/Val group had potentiated startle responses to the CS+. Met allele carrying individuals were characterized by deficient fear conditioning--evidenced by an attenuated startle response to CS+ stimuli. Variation in the BDNF genotype appears related to abnormal fear conditioning, consistent with nonhuman animal work on the importance of BDNF in amygdala-dependent associative learning. The relation between genetic variation in BDNF and amygdala-dependent associative learning deficits is discussed in terms of potential mechanisms of risk for psychopathology.

Disruption of contactin 4 in three subjects with autism spectrum disorder.

BACKGROUND: Autism spectrum disorder (ASD) is a developmental disorder of the central nervous system of largely unknown aetiology. The prevalence of the syndrome underscores the need for biological markers and a clearer understanding of pathogenesis. For these reasons, a genetic study of idiopathic ASD was undertaken. METHODS AND RESULTS: Array based comparative genomic hybridisation identified a paternally inherited chromosome 3 copy number variation (CNV) in three SUBJECTS: a deletion in two siblings and a duplication in a third, unrelated individual. These variations were fluorescence in situ hybridisation (FISH) validated and the end points further delineated using a custom fine tiling oligonucleotide array. Polymerase chain reaction (PCR) products unique to the rearrangements were amplified and sequence analysis revealed the variations to have resulted from Alu Y mediated unequal recombinations interrupting contactin 4 (CNTN4). CONCLUSION: CNTN4 plays an essential role in the formation, maintenance, and plasticity of neuronal networks. Disruption of this gene is known to cause developmental delay and mental retardation. This report suggests that mutations affecting CNTN4 function may be relevant to ASD pathogenesis.

An improved method for generating BAC DNA suitable for FISH.

Fluorescence in situ hybridization (FISH) is commonly used to identify chromosomal aberrations such as translocations, deletions, duplications, gene fusions, and aneuploidies. It relies on the hybridization of fluorescently labeled DNA probes onto denatured metaphase chromosomes or interphase nuclei. These probes are often generated from DNA sequences cloned within bacterial artificial chromosomes (BACs). Growing these BACs in adequate amounts for FISH can be demanding. We describe FISH performed with bacteriophage Phi29 DNA polymerase amplified BAC DNA. Generating this material required significantly smaller cultures and less time than standard methods. The FISH results obtained were comparable with those obtained from standard BAC DNA. We believe this method of BAC DNA generation is useful for the entire FISH community as it improves considerably on prior methods.

Autism and environmental genomics.

Autism spectrum disorders (ASD) are defined by behavior and diagnosed by clinical history and observation but have no biomarkers and are presumably, etiologically and biologically heterogeneous. Given brain abnormalities and high monozygotic concordance, ASDs have been framed as neurobiologically based and highly genetic, which has shaped the research agenda and in particular criteria for choosing candidate ASD genes. Genetic studies to date have not uncovered genes of strong effect, but a move toward "genetic complexity" at the neurobiological level may not suffice, as evidence of systemic abnormalities (e.g. gastrointestinal and immune), increasing rates and less than 100% monozygotic concordance support a more inclusive reframing of autism as a multisystem disorder with genetic influence and environmental contributors. We review this evidence and also use a bioinformatic approach to explore the possibility that "environmentally responsive genes" not specifically associated with the nervous system, but potentially associated with systemic changes in autism, have not hitherto received sufficient attention in autism genetics investigations. We overlapped genes from NIEHS Environmental Genome Project, the Comparative Toxicogenomics Database, and the SeattleSNPs database of genes relevant to the human immune and inflammatory response with linkage regions identified in published autism genome scans. We identified 135 genes in overlap regions, of which 56 had never previously been studied in relation to autism and 47 had functional SNPs (in coding regions). Both our review and the bioinformatics exercise support the expansion of criteria for evaluating the relevance of genes to autism risk to include genes related to systemic impact and environmental responsiveness. This review also suggests the utility of environmental genomic resources in highlighting the potential relevance of particular genes within linkage regions. Environmental responsiveness and systems impacts consistent with system-wide findings in autism are thus supported as important considerations in identifying the numerous and complex modes of gene-environment interaction in autism.