Nataliya Kibiryeva

A challenge of studying mammalian cardiac embryogenesis is the limited ability to perform experimental manipulations in animal models. The avian embryo is widely accepted as a model for mammalian heart developmental studies. In this study, we establish the methodology and protocols for studying the Japanese quail (Coturnix japonica) heart at embryonic day 10 (HH38) using the FUJIFILM VisualSonics Vevo 3100 ultrasound system equipped with a MX550D small animal cardiology transducer. These protocols were designed to measure right ventricular wall thickness, pulmonary artery diameter, and the outflow velocities of the right ventricular outflow tract (RVOT) and the pulmonary artery (PA), thereby establishing baseline parameters of the normally developing quail morphology. Quail embryos are an ideal model for cardiovascular research due to their short incubation period (16–17 days), experimental accessibility, and strong similarities to mammalian heart development. These developmental similarities include, but are not limited to, looping, chamber septation, and the development of a true four-chamber heart. High-resolution imaging modalities, including ultrasound and optical coherence tomography, enable noninvasive, real-time visualization of cardiac morphology and function throughout development. Echocardiography allows for quantitative and qualitative assessments of myocardial structure and cardiac hemodynamics. The similarity to the mammalian heart, combined with rapid embryogenesis, makes quail embryos a valuable model for investigating congenital heart defects, genetic modifications, and fundamental cardiac developmental processes. In this study, we describe reproducible incubation protocols and baseline echocardiographic parameters used to evaluate morphological and physiological changes in the developing embryonic quail heart on embryonic day 10.

A challenge of studying mammalian cardiac embryogenesis is the limited ability to perform experimental manipulations in animal models. The avian embryo is widely accepted as a model for mammalian heart developmental studies. In this study, we establish the methodology and protocols for studying the Japanese quail (Coturnix japonica) heart at embryonic day 10 (HH38) using the FUJIFILM VisualSonics Vevo 3100 ultrasound system equipped with a MX550D small animal cardiology transducer. These protocols were designed to measure right ventricular wall thickness, pulmonary artery diameter, and the outflow velocities of the right ventricular outflow tract (RVOT) and the pulmonary artery (PA), thereby establishing baseline parameters of the normally developing quail morphology. Quail embryos are an ideal model for cardiovascular research due to their short incubation period (16-17 days), experimental accessibility, and strong similarities to mammalian heart development. These developmental similarities include, but are not limited to, looping, chamber septation, and the development of a true four-chamber heart. High-resolution imaging modalities, including ultrasound and optical coherence tomography, enable noninvasive, real-time visualization of cardiac morphology and function throughout development. Echocardiography allows for quantitative and qualitative assessments of myocardial structure and cardiac hemodynamics. The similarity to the mammalian heart, combined with rapid embryogenesis, makes quail embryos a valuable model for investigating congenital heart defects, genetic modifications, and fundamental cardiac developmental processes. In this study, we describe reproducible incubation protocols and baseline echocardiographic parameters used to evaluate morphological and physiological changes in the developing embryonic quail heart on embryonic day 10.

Small Cajal body-associated RNAs (scaRNAs) are essential for biochemical modification of spliceosomal RNAs and spliceosome function. Changes in scaRNA expression level have been associated with developmental issues, including cancer and congenital heart defects (CHDs), although the mechanism remains unclear. Small Cajal body-associated RNA 1 (scaRNA1) guides pseudouridylation at uridine 89 (Ψ89) of the spliceosomal RNA U2, a highly conserved modification that may be critical for spliceosome function. To investigate the role of scaRNA1 in splicing regulation, CRISPR-Cas9 genome editing was used to introduce targeted deletions in the scaRNA1 locus in HEK293T cells. Edited clones were identified by T7 endonuclease I assay and confirmed by Sanger sequencing. Pseudouridylation at Ψ89 was quantified using CMC-based reverse transcription followed by quantitative PCR, and global mRNA splicing alterations were assessed by RNA sequencing. Clones harboring scaRNA1 disruptions exhibited a significant reduction in Ψ89 pseudouridylation, consistent with impaired scaRNA1 function. Transcriptome analysis (of mRNA from two clones) revealed >300 protein coding genes with significant changes in transcript isoform level, including >100 genes related to RNA-binding activity. These results indicate that scaRNA1 disruption alters spliceosomal function and leads to substantial changes in mRNA splicing. The dysregulated splicing of RNA-binding proteins may impair RNA processing and gene expression programs required for normal development, providing new insight into how noncoding RNA dysfunction may contribute to developmental pathogenesis.

Our previous research identified 12 small Cajal body-specific RNAs (scaRNAs) with reduced expression in the right ventricle in infant patients with tetralogy of Fallot. Likewise, we showed that there were significant changes in mRNA processing in the RV in these patients. ScaRNAs play a crucial role in the biochemical maturation of spliceosomal RNAs (pseudouridylation and 2′-O-methylation). We showed that variations in scaRNA1 levels resulted in changes in alternative splicing in human cells. To investigate further the role that scaRNAs play in mRNA processing, we examine here the impact of knocking down scaRNA1 in quail myoblast cells (Coturnix japonica, a well-established animal model for studying embryonic development). Following the knockdown of scaRNA1, transcriptome analysis revealed that the genes Tjp1, Map3k7, and Sppl2a were alternatively spliced. Growing evidence indicates that alternative splicing of mRNA plays an important role in regulating cell differentiation and tissue development. Our data presented here provide additional support for research to clarify the specific roles that individual scaRNAs play in regulating spliceosome function and mRNA splicing.

Critical illness-related corticosteroid insufficiency (CIRCI) can cause hemodynamic instability in neonates after congenital heart surgery with manifestations that increase morbidity and potential mortality. We retrospectively reviewed neonates who underwent cardiac surgery between August 2018 and July 2020 at a freestanding children’s hospital, had next-generation sequencing performed, and had their cortisol levels drawn as standard clinical care after cardiac surgery. The groups were defined as CIRCI (with a cortisol level ≤ 4.5 mcg/dL) and non-CIRCI (level > 4.5 mcg/dL). The CIRCI group (n = 8) had a 100% incidence of heterozygous gene mutation on STX1A with splicing or loss of function, and this mutation was not found in the non-CIRCI group (n = 8). Additional gene mutations were found in the CIRCI group on RAB6A, ABCA3, SIDT2, and LILRB3, with no incidence in the non-CIRCI group. Three additional mutations were found across the CIRCI group in INPPL1 and FAM189A2 (both splicing and missense), with 12–25% of patients in the non-CIRCI group also displaying these mutations. Novel genetic abnormalities were seen in neonates with symptoms of CIRCI with potential cardiac implications from a gene mutation for STX1A. Compounding effects of additional gene mutations need to be confirmed and explored for potential predisposition to hemodynamic instability during times of stress.

Autism Spectrum Disorder (ASD) has been associated with a complex interplay between genetic and environmental factors. Prenatal stress exposure has been identified as a possible risk factor, although most stress-exposed pregnancies do not result in ASD. The serotonin transporter (SERT) gene has been linked to stress reactivity, and the presence of the SERT short (S)-allele has been shown to mediate the association between maternal stress exposure and ASD. In a mouse model, we investigated the effects of prenatal stress exposure and maternal SERT genotype on offspring behavior and explored its association with maternal microRNA (miRNA) expression during pregnancy. Pregnant female mice were divided into four groups based on genotype (wildtype or SERT heterozygous knockout (Sert-het)) and the presence or absence of chronic variable stress (CVS) during pregnancy. Offspring behavior was assessed at 60 days old (PD60) using the three-chamber test, open field test, elevated plus-maze test, and marble-burying test. We found that the social preference index (SPI) of SERT-het/stress offspring was significantly lower than that of wildtype control offspring, indicating a reduced preference for social interaction on social approach, specifically for males. SERT-het/stress offspring also showed significantly more frequent grooming behavior compared to wildtype controls, specifically for males, suggesting elevated repetitive behavior. We profiled miRNA expression in maternal blood samples collected at embryonic day 21 (E21) and identified three miRNAs (mmu-miR-7684-3p, mmu-miR-5622-3p, mmu-miR-6900-3p) that were differentially expressed in the SERT-het/stress group compared to all other groups. These findings suggest that maternal SERT genotype and prenatal stress exposure interact to influence offspring behavior, and that maternal miRNA expression late in pregnancy may serve as a potential marker of a particular subtype of ASD pathogenesis.