Induction of ventricular fibrillation during programmed ventricular stimulation in a patient with CASQ2 heterozygous mutation.

INTRODUCTION: We report the case of a 37-year-old male athlete, who developed during exercise atrial and ventricular arrhythmias. No structural heart disease. RESULTS: Invasive programmed ventricular stimulation induced ventricular fibrillation. A heterozygous mutation in the CASQ2 gene (c.775G>T, p.E259X) was found. CONCLUSIONS: The findings in our patient may suggest some increased ventricular excitability using programmed ventricular stimulation in CASQ2 polymorphic ventricular tachycardia patients.

Investigation of a Large Kindred Reveals Cardiac Calsequestrin (CASQ2) as a Cause of Brugada Syndrome.

BACKGROUND: Brugada syndrome (BrS) is an inherited primary channelopathy syndrome associated with the risk of ventricular fibrillation (VF) and sudden cardiac death in a structurally normal heart. AIM OF THE STUDY: The aim of this study was to clinically and genetically evaluate a large family with severe autosomal dominant Brugada syndrome. METHODS: Clinical and genetic studies were performed. Genetic analysis was conducted with NGS technologies (WES) using the Illumina instrument. According to the standard procedure, variants found by WES were confirmed in all available families by Sanger sequencing. The effect of the variants was studied by using in silico prediction of pathogenicity. RESULTS: The proband was a 52-year-old man who was admitted to the emergency department for syncope at rest. WES of the index case identified a heterozygous VUS CASQ2, c.532T>C, p.(Tyr178His). We studied the segregation of the variation in all pedigree members. All the patients were heterozygous for the variation CASQ2 p.(Tyr178His), whereas the remaining healthy individuals in the family were homozygous for the normal allele. Structural analysis of CASQ2 p.(Tyr178His) was performed and revealed an important effect of the missense variation on monomer stability. The CASQ2 Tyr180 residue is located inside the sarcoplasmic reticulum (SR) junctional face membrane interaction domain and is predicted to disrupt filamentation. CONCLUSIONS: Our data suggest that the p.Tyr178His substitution is associated with BrS in the family investigated, affecting the stability of the protein, disrupting filamentation at the interdimer interface, and affecting the subsequent formation of tetramers and polymers that contain calcium-binding sites.

Catecholaminergic polymorphic ventricular tachycardia (and seizure) caused by a novel homozygous likely pathogenic variant in CASQ2 gene.

BACKGROUND: Although structural heart disease is frequently present among patients who experience sudden cardiac death (SCD), inherited arrhythmia syndromes can also play an important role in the occurrence of SCD. CPVT2, which is the second-most prevalent form of CPVT, arises from an abnormality in the CASQ2 gene. OBJECTIVE: We represent a novel CASQ2 variant that causes CPVT2 and conduct a comprehensive review on this topic. METHODS: The proband underwent Whole-exome sequencing (WES) in order to ascertain the etiology of CPVT. Subsequently, the process of segregating the available family members was carried out through the utilization of PCR and Sanger Sequencing. We searched the google scholar and PubMed/Medline for studies reporting CASQ2 variants, published up to May 10,2023. We used the following mesh term "Calsequestrin" and using free-text method with terms including "CASQ2","CASQ2 variants", and "CASQ2 mutation". RESULTS: The CASQ2 gene was found to contain an autosomal recessive nonsense variant c.268_269insTA:p.Gly90ValfsTer4, which was identified by WES. This variant was determined to be the most probable cause of CPVT in the pedigree under investigation. CONCLUSION: CASQ2 variants play an important role in pathogenesis of CPVT2. Notabely, based on results of our study and other findings in the literature the variant in this gene may cause an neurological signs in the patients with CPVT2. Further studies are needed for more details about the role of this gene in CPVT evaluation, diagnosis, and gene therapy.

CASQ1-related myopathy: The first report from China and the literature review.

Calsequestrin 1 (CASQ1) is the most crucial Ca2+ binding protein localized in the sarcoplasmic reticulum (SR) of skeletal muscle. With high capacity and low affinity for Ca2+, CASQ1 plays a significant role in maintaining a large amount of Ca2+ necessary for muscle contraction. However, only five mutations in CASQ1 have been identified to date. Here, we report a 42-year-old Chinese female patient who presented with a 12 years history of slowly progressive upper limb weakness, predominantly affecting distal muscles, which was uncommon comparing to other CASQ1-related patients. Next-generation sequencing (NGS) analysis revealed a novel heterozygous mutation (c.766G > A, p.Val256Met) in CASQ1. Functional studies confirmed the likely pathogenicity of this variant. Muscle histopathology revealed rare optically empty vacuoles in myofibers and atypical eosinophilic granules in the cytoplasm, which has not been observed before. We also performed a literature review on all the pathogenic mutations in CASQ1 and summarized their genetic and clinical characteristics. This is the first report on CASQ1-related myopathy from China, further expanding the mutation spectrum of CASQ1 gene and provides new insights into the function of CASQ1.

Ablation of Calsequestrin-1, Ca2+ unbalance, and susceptibility to heat stroke.

Introduction: Ca2+ levels in adult skeletal muscle fibers are mainly controlled by excitation-contraction (EC) coupling, a mechanism that translates action potentials in release of Ca2+ from the sarcoplasmic reticulum (SR) release channels, i.e. the ryanodine receptors type-1 (RyR1). Calsequestrin (Casq) is a protein that binds large amounts of Ca2+ in the lumen of the SR terminal cisternae, near sites of Ca2+ release. There is general agreement that Casq is not only important for the SR ability to store Ca2+, but also for modulating the opening probability of the RyR Ca2+ release channels. The initial studies: About 20 years ago we generated a mouse model lacking Casq1 (Casq1-null mice), the isoform predominantly expressed in adult fast twitch skeletal muscle. While the knockout was not lethal as expected, lack of Casq1 caused a striking remodeling of membranes of SR and of transverse tubules (TTs), and mitochondrial damage. Functionally, CASQ1-knockout resulted in reduced SR Ca2+ content, smaller Ca2+ transients, and severe SR depletion during repetitive stimulation. The myopathic phenotype of Casq1-null mice: After the initial studies, we discovered that Casq1-null mice were prone to sudden death when exposed to halogenated anaesthetics, heat and even strenuous exercise. These syndromes are similar to human malignant hyperthermia susceptibility (MHS) and environmental-exertional heat stroke (HS). We learned that mechanisms underlying these syndromes involved excessive SR Ca2+ leak and excessive production of oxidative species: indeed, mortality and mitochondrial damage were significantly prevented by administration of antioxidants and reduction of oxidative stress. Though, how Casq1-null mice could survive without the most important SR Ca2+ binding protein was a puzzling issue that was not solved. Unravelling the mystery: The mystery was finally solved in 2020, when we discovered that in Casq1-null mice the SR undergoes adaptations that result in constitutively active store-operated Ca2+ entry (SOCE). SOCE is a mechanism that allows skeletal fibers to use external Ca2+ when SR stores are depleted. The post-natal compensatory mechanism that allows Casq1-null mice to survive involves the assembly of new SR-TT junctions (named Ca2+ entry units) containing Stim1 and Orai1, the two proteins that mediate SOCE.

Pacing Dynamics Determines the Arrhythmogenic Mechanism of the CPVT2-Causing CASQ2G112+5X Mutation in a Guinea Pig Ventricular Myocyte Computational Model.

Calsequestrin Type 2 (CASQ2) is a high-capacity, low-affinity, Ca2+-binding protein expressed in the sarcoplasmic reticulum (SR) of the cardiac myocyte. Mutations in CASQ2 have been linked to the arrhythmia catecholaminergic polymorphic ventricular tachycardia (CPVT2) that occurs with acute emotional stress or exercise can result in sudden cardiac death (SCD). CASQ2G112+5X is a 16 bp (339-354) deletion CASQ2 mutation that prevents the protein expression due to premature stop codon. Understanding the subcellular mechanisms of CPVT2 is experimentally challenging because the occurrence of arrhythmia is rare. To obtain an insight into the characteristics of this rare disease, simulation studies using a local control stochastic computational model of the Guinea pig ventricular myocyte investigated how the mutant CASQ2s may be responsible for the development of an arrhythmogenic episode under the condition of ß-adrenergic stimulation or in the slowing of heart rate afterward once ß-adrenergic stimulation ceases. Adjustment of the computational model parameters based upon recent experiments explore the functional changes caused by the CASQ2 mutation. In the simulation studies under rapid pacing (6 Hz), electromechanically concordant cellular alternans appeared under ß-adrenergic stimulation in the CPVT mutant but not in the wild-type nor in the non-ß-stimulated mutant. Similarly, the simulations of accelerating pacing from slow to rapid and back to the slow pacing did not display alternans but did generate early afterdepolarizations (EADs) during the period of second slow pacing subsequent acceleration of rapid pacing.

Expression of Genes and Proteins of the Sarcoplasmic Reticulum Са2+-Transport Systems in Cardiomyocytes in Concomitant Coronary Heart Disease and Type 2 Diabetes Mellitus.

We compared the expression of Са2+-ATPase (SERCA2a), calsequestrin (CASQ2), ryanodine receptors (RyR2) proteins and their genes (ATP2A2, CASQ2, and RYR2) in coronary heart disease (CHD) patients with and without comorbid type 2 diabetes mellitus. All studies were performed on the right atrial appendages resected during coronary bypass surgeries. Expression of SERCA2a and RyR2 proteins and their ATP2A2 (p=0.046) and RYR2 genes in comorbid pathology was significantly (p=0.042) higher (by 1.2 and 2 times; p=0.025). The expression of CASQ2 protein and its gene did not differ significantly between the groups (p=0.82 and p=0.066, respectively). It was concluded that the expression of SERCA2a and RyR2 proteins and their genes (but not CASQ2 and its gene) is elevated in CHD associated with type 2 diabetes mellitus. Expression of the studied proteins correlated with the expression of their genes. Increased expression of CASQ2 protein and its gene can probably prevent imbalance of the Ca2+-transporting systems in cardiomyocytes and contractile dysfunction of the myocardium, even in CHD associated with type 2 diabetes mellitus.

Calsequestrin 1 Is an Active Partner of Stromal Interaction Molecule 2 in Skeletal Muscle.

Calsequestrin 1 (CASQ1) in skeletal muscle buffers and senses Ca2+ in the sarcoplasmic reticulum (SR). CASQ1 also regulates store-operated Ca2+ entry (SOCE) by binding to stromal interaction molecule 1 (STIM1). Abnormal SOCE and/or abnormal expression or mutations in CASQ1, STIM1, or STIM2 are associated with human skeletal, cardiac, or smooth muscle diseases. However, the functional relevance of CASQ1 along with STIM2 has not been studied in any tissue, including skeletal muscle. First, in the present study, it was found by biochemical approaches that CASQ1 is bound to STIM2 via its 92 N-terminal amino acids (C1 region). Next, to examine the functional relevance of the CASQ1-STIM2 interaction in skeletal muscle, the full-length wild-type CASQ1 or the C1 region was expressed in mouse primary skeletal myotubes, and the myotubes were examined using single-myotube Ca2+ imaging experiments and transmission electron microscopy observations. The CASQ1-STIM2 interaction via the C1 region decreased SOCE, increased intracellular Ca2+ release for skeletal muscle contraction, and changed intracellular Ca2+ distributions (high Ca2+ in the SR and low Ca2+ in the cytosol were observed). Furthermore, the C1 region itself (which lacks Ca2+-buffering ability but has STIM2-binding ability) decreased the expression of Ca2+-related proteins (canonical-type transient receptor potential cation channel type 6 and calmodulin 1) and induced mitochondrial shape abnormalities. Therefore, in skeletal muscle, CASQ1 plays active roles in Ca2+ movement and distribution by interacting with STIM2 as well as Ca2+ sensing and buffering.

Identification and Characterization of Influential Factors in Susceptibility to Attention Deficit Hyperactivity Disorder Among Preschool-Aged Children.

Attention deficit hyperactivity disorder (ADHD) is the most common childhood-onset neurodevelopmental disorder. Currently, increasing amounts of attention have been focused on the epidemiologic profiling of ADHD in children, viewed as a continuously distributed risk dimension throughout the whole lifespan. This study aimed to identify and characterize potential influential factors susceptible to ADHD-related symptoms among preschool-aged children. A comprehensive questionnaire was self-designed for both children and their parents or guardians and was distributed to 30 kindergartens from Beijing and Hebei, collecting potential influential factors in susceptibility to ADHD. ADHD was assessed by the Conner's Abbreviated Symptom Questionnaire (C-ASQ), and 7,938 children were analyzed. Least absolute shrinkage and selection operator (LASSO) regression and hierarchical degree of adjustment were used to control possible covariates. Five factors, namely, children's secondhand smoking exposure, breastfeeding duration, sleep mode, maternal pregnancy smoking exposure, and parental self-rating for patience, were identified to be independently and significantly associated with ADHD susceptibility. Meanwhile, dose-response relationships were observed between breastfeeding duration, parental self-rating for patience, and ADHD-related symptoms. Finally, a nomogram model was created for predicting ADHD susceptibility based on significant and conventional attributes under each criterion.

Association of T66A polymorphism in CASQ2 with PR interval in a Chinese population.

OBJECTIVE: The aim of this study was to explore the relationship between arrhythmia-associated or electrocardiogram (ECG)-associated common variants and PR interval, QRS duration, QTcorrected, and heart rate in a Chinese cohort. METHODS: We studied the association between 26 single-nucleotide polymorphisms (SNPs) and digital ECG data from 379 unrelated Han Chinese individuals collected in an epidemiological survey in Beijing. All subjects were 45 years of age or older and were free of cardiovascular diseases and diabetes. The SNPs were genotyped in a multiplex panel using the Sequenom MassARRAY platform. RESULTS: Missense variant T66A (Thr66Ala, rs4074536) of the CASQ2 gene, which was previously reported to be associated with QRS complex in European populations, was significantly associated with PR interval prolongation in our sample (padjusted = 0.006, betaadjusted = 3.983 ms). A two-tailed t test showed that the CC genotype (n = 86) had a significantly longer PR interval (162.9 ± 19.4 ms) than the non-CC genotypes (n = 288, PR interval: 154.6 ± 20.9 ms), with a remarkable difference of 8.2 ms between the groups (p = 0.001). Interestingly, this association between T66A of CASQ2 and PR interval was more evident in females (padjusted = 0.007, betaadjusted = 5.723 ms) than in males (padjusted = 0.177, betaadjusted = 2.725 ms). In addition, rs3822714 in the HAND1 locus might be associated with QRS duration (padjusted = 0.034, betaadjusted = -2.268 ms). CONCLUSION: We identified a novel signal of an association between the CC genotype of T66A in CASQ2 and PR interval prolongation in a Chinese population, particularly in females. This association deserves further exploration given its possible effects on calcium handling in cardiac electrophysiology.

Evaluation of the use of SYBR-14 and propidium iodide stain in a fluorescent computer-assisted spermatozoal quantification method in dogs.

The aim of this study was to evaluate the use of SYBR-14/propidium iodide (PI) stain in a computer-assisted spermatozoal quantification (CASQ) method of determining spermatozoal concentration in canine semen. In Experiment A, the spermatozoal concentration was measured (n = 52) with a haemocytometer and by CASQ under fluorescent illumination using green long-pass (G-LP) and red long-pass filters at measurement concentrations of <25 million/ml. For the red filter, the limits of agreement between the haemocytometer and CASQ were -6.3% to 6.8% and -7.5% to 6.2% between the haemocytometer and CASQ for the G-LP filter. For the red filter, the mean precision CVs were 2.21% ± 4.33% (mean ± 95% CI) for the haemocytometer, 2.19% ± 4.29% for CASQ and using the G-LP filter 2.13% ± 4.18% for the haemocytometer and 2.66% ± 5.21% for CASQ. In Experiment B, spermatozoa were also examined with a green spectrum short-pass (G-SP) filter (n = 50) at measurement concentrations of <12.5 million/ml. The limits of agreement between the haemocytometer and CASQ were -5.4% to 7.8% using the red filter, -15.8% to 14.3% using the G-LP filter and -13.1% to 11.3% using the G-SP filter. The mean precision CVs for the haemocytometer and CASQ, respectively, were 2.68% ± 5.26% (mean ± 95% CI) and 1.93% ± 3.72% using the red filter and 2.01% ± 3.95% and 3.55% ± 6.95% using the G-LP filter, and 3.96% ± 7.76% for CASQ using the G-SP filter. Using the red filter, the agreement between the haemocytometer and CASQ and the precision of both haemocytometer methods and CASQ were better than when using green filters. The CASQ method performed using green filters produced acceptable results; however, CASQ using a red filter with PI staining alone was superior to that using green filters and SYBR-14/PI staining.

Luminal Ca2+ regulation of RyR1 Ca2+ channel leak activation and inactivation in sarcoplasmic reticulum membrane vesicles.

In this study, we tested the hypothesis that the RyR1 Ca2+ channel closure is sensitive to outward trans-SR membrane Ca2+ gradients established by SERCA1 pumping. To perform these studies, we employed stopped-flow rapid-kinetic fluorescence methods to measure and assess how variation in trans-SR membrane Ca2+ distribution affects evolution of RyR1 Ca2+ leaks in RyR1/ CASQ1/SERCA1-rich membrane vesicles. Our studies showed that rapid filling of a Mag-Fura-2-sensitive free Ca2+ pool during SERCA1-mediated Ca2+ sequestration appears to be a crucial condition allowing RyR1 Ca2+ channels to close once reloading of luminal Ca2+ stores is complete. Disruption in the filling of this pool caused activation of Ruthenium Red inhibitable RyR1 Ca2+ leaks, suggesting that SERCA1 pump formation of outward Ca2+ gradients is an important aspect of Ca2+ flux control channel opening and closing. In addition, our observed ryanodine-induced shift in luminal Ca2+ from free to a CTC-Ca+-sensitive, CASQ1-associated bound compartment underscores the complex organization and regulation of SR luminal Ca2+. Our study provides strong evidence that RyR1 functional states directly and indirectly influence the compartmentation of luminal Ca2+. This, in turn, is influenced by the activity of SERCA1 pumps to fill luminal pools while synchronously reducing Ca2+ levels on the cytosolic face of RyR1 channels.

Molecular adaptation to calsequestrin 2 (CASQ2) point mutations leading to catecholaminergic polymorphic ventricular tachycardia (CPVT): comparative analysis of R33Q and D307H mutants.

Homozygous calsequestrin 2 (CASQ2) point mutations leads to catecholaminergic polymorphic ventricular tachycardia: a common pathogenetic feature appears to be the drastic reduction of mutant CASQ2 in spite of normal transcription. Comparative biochemical analysis of R33Q and D307H knock in mutant mice identifies different pathogenetic mechanisms for CASQ2 degradation and different molecular adaptive mechanisms. In particular, each CASQ2 point mutation evokes specific adaptive cellular and molecular processes in each of the four adaptive pathways investigated. Thus, similar clinical phenotypes and identical cellular mechanism for cardiac arrhythmia might imply different molecular adaptive mechanisms.

Clinical and genetic investigation of catecholaminergic polymorphic ventricular tachycardia in a consanguineous Tunisian family.

Background: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare disease presenting with syncopal events and sudden cardiac death at a young age in the absence of structural heart disease. Two major genes have been shown to be responsible for CPVT: RYR2 and CASQ2 genes involved in calcium homeostasis.Methods: We report here clinical and molecular investigation of a consanguineous Tunisian family including three affected members. Involvement of RYR2 and CASQ2 genes was investigated.Results: Mutation screening for RYR2 gene showed that no mutation were detected in the coding sequence. A novel variation c.572C/T was identified in CASQ2 gene leading to a p.Pro191Leu.Conclusion: To our knowledge, this is the first clinical and genetic investigation of CPVT in North Africa.

CASQ2 variants in Chinese children with catecholaminergic polymorphic ventricular tachycardia.

BACKGROUND: Biallelic variants of the CASQ2 are known to cause the autosomal recessive form of catecholaminergic polymorphic ventricular tachycardia (CPVT), an inherited disease that predisposes young individuals to syncope and sudden cardiac death. To date, only about 24 CASQ2 variants have been reported in association with CPVT pathogenesis; furthermore, studies in Asians, especially in the Chinese population, are relatively rare. The aim of this study was to detect CASQ2 variants in Chinese patients with CPVT. METHODS: We used targeted next-generation sequencing (NGS) to identify CASQ2 variants in Chinese patients with CPVT. A screening process was performed to prioritize rare variants of potential functional significance. Sanger sequencing was conducted to conform the candidate variants and determine the parental origin. RESULTS: We identified seven different CASQ2 variants, of which three (c.1074_1075delinsC, c.1175_1178delACAG, and c.838+1G>A) have not been previously reported. The variants exhibited autosomal recessive inheritance, and were detected in four unrelated Chinese families with CPVT. They included a nonsense variant c.97C>T (p.R33*) and a missense variant c.748C>T (p.R250C) in Family 1 with three CPVT patients; two heterozygous frameshift variants, c.1074_1075delinsC (p.G359Afs*12) and c.1175_1178delACAG (p.D392Vfs*84), in Family 2 with one CPVT patient; one pathogenic homozygous variant c.98G>A (p.R33Q) of CASQ2 in the CPVT patient of Family 3; and two heterozygous splicing variants, (c.532+1G>A) and (c.838+1G>A), in Family 4 with one CPVT patient. CONCLUSION: To our knowledge, this is the first systematic study of Chinese children with CASQ2 variants. Our work further expands the genetic spectrum of CASQ2-associated CPVT.

Efficacy of Flecainide in Catecholaminergic Polymorphic Ventricular Tachycardia Is Mutation-Independent but Reduced by Calcium Overload.

BACKGROUND: The dual Na+ and cardiac Ca2+-release channel inhibitor, Flecainide (FLEC) is effective in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT), a disease caused by mutations in cardiac Ca2+-release channels (RyR2), calsequestrin (Casq2), or calmodulin. FLEC suppresses spontaneous Ca2+ waves in Casq2-knockout (Casq2-/-) cardiomyocytes, a CPVT model. However, a report failed to find FLEC efficacy against Ca2+ waves in another CPVT model, RyR2-R4496C heterozygous mice (RyR2R4496C+/-), raising the possibility that FLEC efficacy may be mutation dependent. OBJECTIVE: To address this controversy, we compared FLEC in Casq2-/- and RyR2R4496C+/- cardiomyocytes and mice under identical conditions. METHODS: After 30 min exposure to FLEC (6 µM) or vehicle (VEH), spontaneous Ca2+ waves were quantified during a 40 s pause after 1 Hz pacing train in the presence of isoproterenol (ISO, 1 µM). FLEC efficacy was also tested in vivo using a low dose (LOW: 3 mg/kg ISO + 60 mg/kg caffeine) or a high dose catecholamine challenge (HIGH: 3 mg/kg ISO + 120 mg/kg caffeine). RESULTS: In cardiomyocytes, FLEC efficacy was dependent on extracellular [Ca2+]. At 2 mM [Ca2+], only Casq2-/- myocytes exhibited Ca2+ waves, which were strongly suppressed by FLEC. At 3 mM [Ca2+] both groups exhibited Ca2+ waves that were suppressed by FLEC. At 4 mM [Ca2+], FLEC no longer suppressed Ca2+ waves in both groups. Analogous to the results in myocytes, RyR2R4496C+/- mice (n = 12) had significantly lower arrhythmia scores than Casq2-/- mice (n = 9), but the pattern of FLEC efficacy was similar in both groups (i.e., reduced FLEC efficacy after HIGH dose catecholamine challenge). CONCLUSION: FLEC inhibits Ca2+ waves in RyR2R4496C+/- cardiomyocytes, indicating that RyR2 channel block by FLEC is not mutation-specific. However, FLEC efficacy is reduced by Ca2+ overload in vitro or by high dose catecholamine challenge in vivo, which could explain conflicting literature reports.

Development of a fluorescent computer-assisted spermatozoal quantification method and a comparison of results for manual counting with a haemocytometer and computer-assisted semen analysis in dogs.

The aim of this study was to develop and validate a novel, computer-assisted spermatozoal quantification (CASQ) method of determining spermatozoal concentration in canine semen. In Experiment A, the spermatozoal concentration was measured (n = 28) with a haemocytometer using light microscopy, CASQ and computer-assisted semen analysis (CASA; MMC sperm), following three independent dilutions. The limits of agreement between the haemocytometer and CASQ were -13.1% to 13.8% and -27.0% to 28.6% between the haemocytometer and CASA. The precision CVs (limits of agreement) were 5.7% (-7.8% to 8.9%) for the haemocytometer, 6.2% (-8.8% to 12.3%) for CASQ and 10.8% (-16.0% to 19.5%) for CASA. In Experiment B, spermatozoa were manually counted (n = 42) with the haemocytometer under fluorescent illumination using the CASQ sample. The limits of agreement between the CASQ and the haemocytometer were satisfactory (-4.6% to 4.6%) and the precision CVs (limits of agreement) were 6.2% (-9.0% to 11.4%) for the haemocytometer and 4.4% (-5.8% to 8.6%) for CASQ. The CASQ method was then clinically applied to compare the haemocytometer (light and fluorescent methods) with CASQ and CASA. Outlying data were removed. These studies demonstrated that CASQ was reliable and that the MMC sperm CASA was unreliable as methods for determining spermatozoal concentration in canine semen. Computer-assisted spermatozoal quantification was also determined to be more precise than manual counting with the haemocytometer. Using the clinical protocol, the agreement between the haemocytometer and CASQ method was acceptable, but it was worse than in the experiments where duplicate samples and a larger volume of semen were analysed. The CASQ method may be a useful method to measure the membrane status of canine spermatozoa; however, further investigation is required. Counting spermatozoa using fluorescent microscopy and the haemocytometer may improve the efficiency of counting and the accuracy of the method.

Delayed Onset of Sleep in Adolescents With PAX6 Haploinsufficiency.

OBJECTIVE: PAX6 haploinsufficiency ( +/-) can occur due to mutations involving only PAX6 in patients with isolated aniridia or as contiguous gene deletions in patients with Wilms tumor, aniridia, genitourinary anomalies, and range of developmental and intellectual disabilities syndrome. Given the role of PAX6 in pineal development and circadian regulation, adolescents with PAX6+/- may experience sleep-wake disturbances. The purpose of this observational study was to explore sleep-related phenotypes in adolescents with PAX6+/-. METHODS: This study compared sleep phenotypes of nine subjects with PAX6+/- (aged 10-19 years) with previously published data on healthy adolescents ( n = 25, aged 10-18 years). Subjects completed the Cleveland Adolescent Sleepiness Questionnaire (CASQ), Patient Reported Outcomes Measurement Information System (PROMIS) Sleep Disturbance (v. 1.0; 8a), and PROMIS Sleep-Related Impairment (v. 1.0; 8b) Questionnaires and wore actigraphs for seven nights to record sleep patterns. RESULTS: Total CASQ, PROMIS sleep-related impairment, and PROMIS sleep disturbance scores were not statistically different between the groups ( ps > .15). Actigraph data for lights off to sleep-onset time were found to be significantly higher in subjects with PAX6+/- versus the healthy comparison group (adjusted mean [95% confidence interval]: 20.1 min [8.1, 49.8] vs. 6.2 min [3.7, 10.4], respectively, p = .04). CONCLUSION: Both adolescents with PAX6+/- and the healthy comparison group on average slept less than 8 hr/night, and overall sleep deprivation in adolescents may have masked differences between groups. This study used rare genetic disorders with biological vulnerability to sleep problems as a genotype-phenotype model. Knowledge of sleep-related phenotypes will assist in designing studies to manage sleep-related symptoms in adolescents.

Interpreting Incidentally Identified Variants in Genes Associated With Catecholaminergic Polymorphic Ventricular Tachycardia in a Large Cohort of Clinical Whole-Exome Genetic Test Referrals.

BACKGROUND: The rapid expansion of genetic testing has led to increased utilization of clinical whole-exome sequencing (WES). Clinicians and genetic researchers are being faced with assessing risk of disease vulnerability from incidentally identified genetic variants which is typified by variants found in genes associated with sudden death-predisposing catecholaminergic polymorphic ventricular tachycardia (CPVT). We sought to determine whether incidentally identified variants in genes associated with CPVT from WES clinical testing represent disease-associated biomarkers. METHODS AND RESULTS: CPVT-associated genes RYR2 and CASQ2 variants were identified in one of the world's largest collections of clinical WES referral tests (N=6517, Baylor Miraca Genetics Laboratories) and compared with a control cohort of ostensibly healthy individuals (N=60 706) and a case cohort of CPVT cases (N=155). Within the WES cohort, the rate of rare variants in CPVT-associated genes was 8.8% compared with 6.0% among controls and 60.0% among cases. There was a predominance of variants of undetermined significance (97.7%). After protein topology mapping, WES variants colocalized more frequently to residues with variants found in controls compared with cases. Retrospective clinical evaluation of individuals referred to our institution with WES-positive variants demonstrated no evidence of clinical CPVT in individuals with a low pretest clinical suspicion for CPVT. CONCLUSIONS: The prevalence of incidentally identified CPVT-associated variants is ≈9% among WES tests. Variants of undetermined significances in CPVT-associated genes in WES genetic testing, in the absence of clinical suspicion for CPVT, are unlikely to represent markers of CPVT pathogenicity.