👤 Jennelle C Hodge

Gastrointestinal (GI) enterochromaffin (EC) cells are specialised sensors of luminal stimuli. They secrete most of the body's serotonin (5-HT), and are critical for modulating GI motility, secretion, and sensation, while also signaling satiety and intestinal discomfort. The aim of this study was to investigate mechanisms underlying the regulation of human EC cells, and the relative importance of direct nutrient stimulation compared with neuronal and paracrine regulation. Intestinal organoids from human duodenal biopsies were modified using CRISPR-Cas9 to specifically label EC cells with either the fluorescent protein Venus or the cyclic adenosine monophosphate (cAMP) sensor Epac1-S-H187. EC cells were purified by fluorescence-activated cell sorting for analysis by bulk RNA sequencing and liquid chromatography mass spectrometry peptidomics. The function of human EC cells was studied using single-cell patch clamp, calcium and cAMP imaging, and 5-hydroxytryptamine (5-HT) enzyme-linked immunosorbent assays (ELISAs). Human EC cells showed expression of receptors for nutrients (including GPR142, GPBAR1, GPR119, FFAR2, OR51E1, OR51E2), gut hormones (including SSTR1,2&5, NPY1R, GIPR) and neurotransmitters (ADRA2A, ADRB1). Functional assays revealed EC responses (calcium, cAMP, and/or secretion) to a range of stimuli, including bacterial metabolites, aromatic amino acids, and adrenergic agonists. Electrophysiological recordings showed that isovalerate increased action potential firing. 5-HT release from EC cells controls many physiological functions and is currently being targeted to treat disorders of the gut-brain axis. Studying ECs from human organoids enables improved understanding of the molecular mechanisms underlying EC cell activation, which is fundamental for the development of new strategies to target 5-HT-related gut and metabolic disorders. Show less

Background Chromosomal microarray analysis (CMA) provides an opportunity to understand genetic causes of congenital heart disease (CHD). The methods for describing cardiac phenotypes in patients with CMA abnormalities have been inconsistent, which may complicate clinical interpretation of abnormal testing results and hinder a more complete understanding of genotype-phenotype relationships. Methods and Results Patients with CHD and abnormal clinical CMA were accrued from 9 pediatric cardiac centers. Highly detailed cardiac phenotypes were systematically classified and analyzed for their association with CMA abnormality. Hierarchical classification of each patient into 1 CHD category facilitated broad analyses. Inclusive classification allowing multiple CHD types per patient provided sensitive descriptions. In 1363 registry patients, 28% had genomic disorders with well-recognized CHD association, 67% had clinically reported copy number variants (CNVs) with rare or no prior CHD association, and 5% had regions of homozygosity without CNV. Hierarchical classification identified expected CHD categories in genomic disorders, as well as uncharacteristic CHDs. Inclusive phenotyping provided sensitive descriptions of patients with multiple CHD types, which occurred commonly. Among CNVs with rare or no prior CHD association, submicroscopic CNVs were enriched for more complex types of CHD compared with large CNVs. The submicroscopic CNVs that contained a curated CHD gene were enriched for left ventricular obstruction or septal defects, whereas CNVs containing a single gene were enriched for conotruncal defects. Neuronal-related pathways were over-represented in single-gene CNVs, including top candidate causative genes Show less

The GPHN gene codes for gephyrin, a key scaffolding protein in the neuronal postsynaptic membrane, responsible for the clustering and localization of glycine and GABA receptors at inhibitory synapses. Gephyrin has well-established functional links with several synaptic proteins that have been implicated in genetic risk for neurodevelopmental disorders such as autism spectrum disorder (ASD), schizophrenia and epilepsy including the neuroligins (NLGN2, NLGN4), the neurexins (NRXN1, NRXN2, NRXN3) and collybistin (ARHGEF9). Moreover, temporal lobe epilepsy has been linked to abnormally spliced GPHN mRNA lacking exons encoding the G-domain of the gephyrin protein, potentially arising due to cellular stress associated with epileptogenesis such as temperature and alkalosis. Here, we present clinical and genomic characterization of six unrelated subjects, with a range of neurodevelopmental diagnoses including ASD, schizophrenia or seizures, who possess rare de novo or inherited hemizygous microdeletions overlapping exons of GPHN at chromosome 14q23.3. The region of common overlap across the deletions encompasses exons 3-5, corresponding to the G-domain of the gephyrin protein. These findings, together with previous reports of homozygous GPHN mutations in connection with autosomal recessive molybdenum cofactor deficiency, will aid in clinical genetic interpretation of the GPHN mutation spectrum. Our data also add to the accumulating evidence implicating neuronal synaptic gene products as key molecular factors underlying the etiologies of a diverse range of neurodevelopmental conditions. Show less

The three members of the human neurexin gene family, neurexin 1 (NRXN1), neurexin 2 (NRXN2), and neurexin 3 (NRXN3), encode neuronal adhesion proteins that have important roles in synapse development and function. In autism spectrum disorder (ASD), as well as in other neurodevelopmental conditions, rare exonic copy-number variants and/or point mutations have been identified in the NRXN1 and NRXN2 loci. We present clinical characterization of four index cases who have been diagnosed with ASD and who possess rare inherited or de novo microdeletions at 14q24.3-31.1, a region that overlaps exons of the alpha and/or beta isoforms of NRXN3. NRXN3 deletions were found in one father with subclinical autism and in a carrier mother and father without formal ASD diagnoses, indicating issues of penetrance and expressivity at this locus. Notwithstanding these clinical complexities, this report on ASD-affected individuals who harbor NRXN3 exonic deletions advances the understanding of the genetic etiology of autism, further enabling molecular diagnoses. Show less