Quantification of mitochondrial acetylation dynamics highlights prominent sites of metabolic regulation

Lysine acetylation is rapidly becoming established as a key post-translational modification for regulating mitochondrial metabolism. Nonetheless, distinguishing regulatory sites from among the thousands identified by mass spectrometry and elucidating how these modifications alter enzyme function remain primary challenges. Here, we performed multiplexed quantitative mass spectrometry to measure changes in the mouse liver mitochondrial acetylproteome in response to acute and chronic alterations in nutritional status, and integrated these data sets with our compendium of predicted Sirt3 targets. These analyses highlight a subset of mitochondrial proteins with dynamic acetylation sites, including acetyl-CoA acetyltransferase 1 (Acat1), an enzyme central to multiple metabolic pathways. We performed in vitro biochemistry and molecular modeling to demonstrate that acetylation of Acat1 decreases its activity by disrupting the binding of coenzyme A. Collectively, our data reveal an important new target of regulatory acetylation and provide a foundation for investigating the role of select mitochondrial protein acetylation sites in mediating acute and chronic metabolic transitions.

Mitochondrial ADCK3 employs an atypical protein kinase-like fold to enable coenzyme Q biosynthesis

The ancient UbiB protein kinase-like family is involved in isoprenoid lipid biosynthesis and is implicated in human diseases, but demonstration of UbiB kinase activity has remained elusive for unknown reasons. Here, we quantitatively define UbiB-specific sequence motifs and reveal their positions within the crystal structure of a UbiB protein, ADCK3. We find that multiple UbiB-specific features are poised to inhibit protein kinase activity, including an N-terminal domain that occupies the typical substrate binding pocket and a unique A-rich loop that limits ATP binding by establishing an unusual selectivity for ADP. A single alanine-to-glycine mutation of this loop flips this coenzyme selectivity and enables autophosphorylation but inhibits coenzyme Q biosynthesis in vivo, demonstrating functional relevance for this unique feature. Our work provides mechanistic insight into UbiB enzyme activity and establishes a molecular foundation for further investigation of how UbiB family proteins affect diseases and diverse biological pathways.

Cerebellar Ataxia and Coenzyme Q Deficiency through Loss of Unorthodox Kinase Activity

The UbiB protein kinase-like (PKL) family is widespread, comprising one-quarter of microbial PKLs and five human homologs, yet its biochemical activities remain obscure. COQ8A (ADCK3) is a mammalian UbiB protein associated with ubiquinone (CoQ) biosynthesis and an ataxia (ARCA2) through unclear means. We show that mice lacking COQ8A develop a slowly progressive cerebellar ataxia linked to Purkinje cell dysfunction and mild exercise intolerance, recapitulating ARCA2. Interspecies biochemical analyses show that COQ8A and yeast Coq8p specifically stabilize a CoQ biosynthesis complex through unorthodox PKL functions. Although COQ8 was predicted to be a protein kinase, we demonstrate that it lacks canonical protein kinase activity in trans. Instead, COQ8 has ATPase activity and interacts with lipid CoQ intermediates, functions that are likely conserved across all domains of life. Collectively, our results lend insight into the molecular activities of the ancient UbiB family and elucidate the biochemical underpinnings of a human disease.

SORCS1 is necessary for normal insulin secretory granule biogenesis in metabolically stressed β cells

We previously positionally cloned Sorcs1 as a diabetes quantitative trait locus. Sorcs1 belongs to the Vacuolar protein sorting-10 (Vps10) gene family. In yeast, Vps10 transports enzymes from the trans-Golgi network (TGN) to the vacuole. Whole-body Sorcs1 KO mice, when made obese with the leptin(ob) mutation (ob/ob), developed diabetes. β Cells from these mice had a severe deficiency of secretory granules (SGs) and insulin. Interestingly, a single secretagogue challenge failed to consistently elicit an insulin secretory dysfunction. However, multiple challenges of the Sorcs1 KO ob/ob islets consistently revealed an insulin secretion defect. The luminal domain of SORCS1 (Lum-Sorcs1), when expressed in a β cell line, acted as a dominant-negative, leading to SG and insulin deficiency. Using syncollin-dsRed5TIMER adenovirus, we found that the loss of Sorcs1 function greatly impairs the rapid replenishment of SGs following secretagogue challenge. Chronic exposure of islets from lean Sorcs1 KO mice to high glucose and palmitate depleted insulin content and evoked an insulin secretion defect. Thus, in metabolically stressed mice, Sorcs1 is important for SG replenishment, and under chronic challenge by insulin secretagogues, loss of Sorcs1 leads to diabetes. Overexpression of full-length SORCS1 led to a 2-fold increase in SG content, suggesting that SORCS1 is sufficient to promote SG biogenesis.

Interaction between insulin and glucose-delivery route in regulation of net hepatic glucose uptake in conscious dogs

In the presence of fixed basal levels of insulin, the route of intravenous glucose delivery (protal vs. peripheral) determines whether net hepatic glucose uptake (NHGU) occurs. Our aims were to determine if the route of intravenous glucose delivery also plays a role in regulating NHGU in the presence of hyperinsulinemia and to determine if length of fast (18 vs. 36 h) influences regulation of NHGU. Five conscious dogs fasted 18 h were given somatostatin and replacement insulin (245 +/- 34 microU.kg-1.min-1) and glucagon (0.65 ng.kg-1.min-1) infusions intraportally. After a 40-min control period, the insulin infusion rate was increased fourfold, and glucose was infused for 3 h. Glucose was given either through a peripheral vein or the portal vein for 90 min to double the glucose load reaching the liver. The order of infusions was randomized. NHGU was measured with the arterial - venous difference technique. Insulin and glucagon levels were 12 +/- 2, 35 +/- 6, and 36 +/- 5 microU/ml and 55 +/- 12, 61 +/- 13, and 59 +/- 7 pg/ml during the control, peripheral, and portal infusions, respectively. The glucose infusion rate, the load of glucose reaching the liver, and the arterial-portal plasma glucose gradient were 0, 9.58 +/- 2.28, and 10.44 +/- 2.94 mg.kg-1.min-1; 29.4 +/- 3.6, 56.8 +/- 3.4, and 56.8 +/- 2.8 mg.kg-1.min-1; and 2 +/- 1, 5 +/- 1, and -51 +/- 15 mg/dl during the same periods.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidemiology of enamel hypoplasia in deciduous teeth: explaining variation in prevalence in western India

This study is based on seven samples of school children (n = 516) from rural (five groups) and urban (two groups) settings in western Maharashtra, India. Height and weight were recorded for each subject. Intra-oral observation of the labial surface of maxillary and mandibular anterior teeth was conducted with a low power (3x) illuminated hand lens. Presence of enamel hypoplasia was recorded on a dental chart by drawing the size and location of the defect on the affected tooth. Data analysis was conducted in two stages: 1) Enamel hypoplasia (EH) prevalence was analyzed by percentage of teeth and by percentage of individuals affected for the composite sample and independently for each study group and 2) an assessment of the relationship between anthropometric variables (height and weight), socio-economic status (SES), and localized hypoplasia of primary canines (LHPC; Skinner, 1986) was evaluated using multiple linear regression analysis. EH was observed less often in deciduous incisors (0.2% in di(2) to 2.5% in di(2)) than in deciduous canines (dc). Mandibular dc were affected with the greatest frequency (23.1%, tooth count). The overall individual count prevalence of dc hypoplasia (LHPC) is 26.2% (134/511) for all village samples and sexes combined. Difference in LHPC frequency by sex is non-significant, with males (24.7%, 70/284) and females (28.2%, 64/227) exhibiting nearly equal values. Significant inter-group variation in LHPC prevalence was documented among the seven groups, and the range of LHPC prevalence the among living groups exceeds variability in LHPC among four prehistoric Chalcolithic skeletal series of the Deccan Plateau. Multiple regression analysis revealed no significant relationship between height-for-age or weight-for-age in four school samples (two urban/two rural), but a significant association between stature and LHPC was found for three rural endogamous groups. Children with LHPC were significantly shorter by 1.5 cm than children who lacked the defect after controlling for differences in age. While the association between low birth weight and EH is strong and well documented clinically, the association between childhood stature and LHPC is more variable across groups and may reflect inter-group variation in the duration and intensity of environmental stress.

Systems Biochemistry Approaches to Defining Mitochondrial Protein Function

Defining functions for the full complement of proteins is a grand challenge in the post-genomic era and is essential for our understanding of basic biology and disease pathogenesis. In recent times, this endeavor has benefitted from a combination of modern large-scale and classical reductionist approaches-a process we refer to as "systems biochemistry"-that helps surmount traditional barriers to the characterization of poorly understood proteins. This strategy is proving to be particularly effective for mitochondria, whose well-defined proteome has enabled comprehensive analyses of the full mitochondrial system that can position understudied proteins for fruitful mechanistic investigations. Recent systems biochemistry approaches have accelerated the identification of new disease-related mitochondrial proteins and of long-sought "missing" proteins that fulfill key functions. Collectively, these studies are moving us toward a more complete understanding of mitochondrial activities and providing a molecular framework for the investigation of mitochondrial pathogenesis.

Focused life history data and linear enamel hypoplasia to help explain intergenerational variation in relative leg length within Taiwanese families

This study first examines the hypothesis that significant intergeneration increases in stature within 85 Taiwanese families in two study locations were primarily the result of increases in subischial leg length. It then evaluates a second hypothesis that independent assessments of the extent of intergenerational change in childhood environments within these families helped account for parent-offspring differences in relative leg length. Childhood environments were assessed using two criteria: developmental environment scores derived from life history data and evidence of linear enamel hypoplasia (LEH). Relative leg length was represented in two ways, as either the difference between internally estimated sex-specific z-scores of sitting height and subischial leg length (z(D) = z(SH) - z(LL)) or as relative sitting height (RSH; sitting height/height x 100). Paired Student t tests indicated intergenerational increases in relative leg length were significantly greater than zero in both study locations (P < or = 0.012). The second hypothesis, tested using a hierarchical model with maximum likelihood estimation that allowed for nesting of more than one offspring per family, received support as midparent-offspring differences in composite scores were significantly positively associated with midparent-offspring differences in relative leg length. This was true alone (P = 0.018), and when significant associations with LEH prevalence among mothers and offspring were statistically controlled for (P = 0.010). Evidence also indicated that while the large majority of offspring were taller than their midparental average height (84.3%; 91/108), offspring who were taller were also more likely to have relatively longer legs than by chance alone (Fishers exact, P = 0.027).

Linear enamel hypoplasia and growth in an Australian Aboriginal community: not so small, but not so healthy either

BACKGROUND

While much is strongly suspected about synergisms linking courses of growth and development with nutrient intakes, immune function, disease exposures, and energy expenditures, debates remain regarding the probability of permanent impairments to growth and function under various circumstances.

AIM

This study tests a series of related hypotheses in an attempt to reconcile evidence of increasing physiological stress among Warlpiri and Pintubi infants and young children following settlement in the 1940s with their frequently rapid and undelayed longitudinal growth in stature during adolescence.

SUBJECTS AND METHODS

The study used archived cross-sectional and longitudinal records of stature, weight, and dental casts collected by the Dental School at the University of Adelaide beginning in 1951 at the then recently settled community of Yuendumu. Longitudinal modelling of height data and all statistical tests were accomplished using SYSTAT 10. Height, weight, and BMI (kg m-2) for age z-scores were calculated using NCHS reference data. Dental casts were scored for linear enamel hypoplasia (LEH) with each defect assigned to an enamel developmental unit. The extent of height catch-up was estimated using conditional height gain.

RESULTS

Cross-sectional analyses indicate significant associations between birth year and women's heights (n = 105, p = 0.02) or height for age z-scores (p = 0.003), but no similar associations among men. Final height for age z-score was significantly associated with sex (p < 0.0005), onset (p = 0.031), and an onset by number of enamel defects interaction (p = 0.033). Late adolescent height z-scores were only significantly negatively associated with increasing numbers of defects among individuals with enamel defects appearing prior to about 18 months of age (n = 60, p = 0.019). With longitudinally estimated age at peak height velocity (APHV) statistically controlled, peak height velocity (PHV) was similarly significantly positively associated with conditional height gain in males (n = 50, p = 0.01) and females (n = 31, p = 0.05). Exploratory analyses suggest that with timing and intensity of PHV controlled, childhood body mass was only significantly positively associated with catch-up in height among those who experienced defect onset relatively early (n = 80, p = 0.005).

CONCLUSION

Results help explain previously documented, and apparently contradictory, outcomes of settlement processes. Rapid and relatively undelayed late childhood and adolescent growth associated with catch-up in height occurred through a confluence of increasing early childhood systemic stress followed by increases in net energy consumption that probably increased as children aged.

Problems in accurate medical diagnosis of depression in female patients

Research in women's health has revealed the difficulties female patients experience in their attempts to receive accurate medical diagnoses. Depression may be misdiagnosed in 30-50% of female patients. This difficulty is considerably enhanced when women have physical diseases characterized by symptoms that resemble a major depressive disorder. In addition, medical treatments may induce symptoms that are misdiagnosed as affective distress. Multiple causes contribute to an enhanced likelihood of misdiagnoses in women, including physicians' androcentrically orientated medical training and the two-to-one female-to-male ratio of depression treatment. The adverse consequences of incorrect diagnoses range from unnecessary expenditures of a woman's resources to potentially life-threatening medical conditions. Ironically, medical misdiagnoses of physical conditions may induce depressive reactions in female patients. A woman's age, sexual orientation, menstrual, occupational, and/or parental status represent potential areas of discrimination in diagnostic determinations. Suggestions are offered for improving the accuracy of health care providers' diagnoses in women.

Intergenerational gains in relative knee height as compared to gains in relative leg length within Taiwanese families

Evidence indicates that variation in relative leg length (RLL) is a sensitive indicator of early childhood circumstances, but research presents conflicting evidence of how lower leg growth contributes to variability. This study investigates the extent of intergenerational changes in subischial leg length and knee height relative to stature among father-son, mother-daughter, and midparent-offspring pairs. These changes and differences in the extent of mean change in the two indices within like-sex parent-offspring pairs were assessed using repeated measures ANOVA. Results indicate that within all categories, mean generational differences in both indices were substantial [Delta RLL z: 0.64-0.73; Delta relative knee height (RKH) z: 0.46-0.64] and statistically significant (P < or = 0.010). Mean increases in RLL and RKH across parent-offspring categories were consistently greater in Taipei than Auckland, though only the midparent-offspring generation by location contrast for RLL was statistically significant (P = 0.037). Father-son and mother-daughter average differences were virtually identical for RLL (0.73 z vs. 0.72 z). When differences within pairs in the extent of change in RLL and RKH were assessed directly, mother-daughter mean differences approached significance at an alpha level of 0.05 (Delta = 0.26 z; F = 3.42, df = 1, 42, P = 0.071). Father-son differences were smaller (Delta = 0.09 z) and statistically insignificant suggesting very similar amounts of change in the two indices.

The contribution of adolescent growth to shorter adult statures among girls of Chinese ancestry

Researchers have hypothesized that shorter mean statures at onset of the adolescent spurt and more rapid skeletal maturation during adolescence among East Asian populations contribute significantly to their shorter mean adult statures compared to European populations. The goal of this study is to use longitudinal height growth data modeled with the Preece-Baines Model 1 (PB1) function to examine the relative importance of adolescent growth to population differences in adult stature. Biological variables for 303 Chinese females from the Da-an District in Taipei, Taiwan, are compared with those for 23 British and 69 Euro-American females. Results indicate that 96% of the difference in adult statures (4.37 cm) between the British and urban Chinese may be attributed to the greater amount of time available to the British for preadolescent growth. Growth during adolescence between these two groups is not significantly different. When comparisons are made with the Euro-American sample from Berkeley, California, only about 26% of the difference in adult stature (6.96 cm) may be attributed to the later age at take-off. Much (53.2%) of the difference has already accrued by take-off among the Chinese. Small, but statistically significant differences in adolescent growth also exist. When considered within the context of other longitudinal studies of European and American females, this study gives only modest support to the hypothesis that more rapid skeletal maturation leads to reduced amounts of adolescent growth among East Asian populations. Interestingly, though, population differences do appear to exist in the relationship between the relative timing of an individual's growth spurt and spurt intensity. Am. J. Hum. Biol. 10:735-746, 1998. © 1998 Wiley-Liss, Inc.

Patrilineal family values, family planning and variation in stature among Taiwanese six-year-olds

It has been argued that patrilineal joint family systems tend to bias family planning decisions in favour of sons. A simple model suggests that in such societies, any given son will be more highly valued by his parents (1) the fewer his brothers and (2) the earlier his birth is in the brother series. A daughter's value will be greater (1) the fewer brothers she has and (2) the earlier her birth is relative to other sisters. This study first addresses the extent of son preference as inferred from family composition data for 772 Taiwanese first-graders born in the mid-1970s in two socioeconomically distinct communities in Taipei, Taiwan. It then uses linear regression to consider whether the model criteria help account for statural variation among children in each study area when controlling for differences in measurement age, parental education and housing. With respect to family composition and gender preference, available evidence was consistent with previous surveys. While better-educated parents in the more affluent study area had significantly fewer children (p < 0.0005) and were more willing to stop without a son, girls there, as in the less affluent area, were still significantly more likely than boys to belong to large sibships (p < or = 0.005). Evidence from mean height of males and females partially accords with hypothetical predictions. In the less affluent area, the interaction effect of male birth order and the presence of younger siblings was significantly associated with mean stature (p = 0.002). Males without brothers were 2.0 cm taller than males with either an older or a younger brother (116.3 +/- 0.5 cm vs 114.3 +/- 0.4 cm). Males who had both younger and older brothers, but often no sisters, were about as tall, however, as those without brothers. A similar, but less pronounced, pattern was found among males in the more affluent area, but only among those who had sisters. These boys were also consistently shorter than boys without sisters (115.6 +/- 0.6 cm vs 117.7 +/- 0.6 cm; p = 0.001). Patterns of mean female stature did not clearly support the hypothesis. Girls in the more affluent area were relatively tall and did not show significant variation. Results among less affluent girls showed significant contrasts, but not necessarily in the predicted direction.

Prolyl endopeptidase-like is a (thio)esterase involved in mitochondrial respiratory chain function

Deficiency of the serine hydrolase prolyl endopeptidase-like (PREPL) causes a recessive metabolic disorder characterized by neonatal hypotonia, feeding difficulties, and growth hormone deficiency. The pathophysiology of PREPL deficiency and the physiological substrates of PREPL remain largely unknown. In this study, we connect PREPL with mitochondrial gene expression and oxidative phosphorylation by analyzing its protein interactors. We demonstrate that the long PREPLL isoform localizes to mitochondria, whereas PREPLS remains cytosolic. Prepl KO mice showed reduced mitochondrial complex activities and disrupted mitochondrial gene expression. Furthermore, mitochondrial ultrastructure was abnormal in a PREPL-deficient patient and Prepl KO mice. In addition, we reveal that PREPL has (thio)esterase activity and inhibition of PREPL by Palmostatin M suggests a depalmitoylating function. We subsequently determined the crystal structure of PREPL, thereby providing insight into the mechanism of action. Taken together, PREPL is a (thio)esterase rather than a peptidase and PREPLL is involved in mitochondrial homeostasis.

The process of adapting a sexual health intervention for Black early adolescents: a stakeholder engagement approach

Young Black women are disproportionately affected by sexually transmitted infections (STIs) and HIV. Notably, few sexual health interventions for Black girls have documented the process of utilizing stakeholder input from the Black community to culturally tailor content. We conducted formative work in Chicago to adapt a mother-daughter HIV/STI prevention intervention originally designed for Black adolescent girls aged 14-18 years to meet the needs of early adolescent girls aged 11-13 years. Our iterative process involved three phases: (i) soliciting feedback from an expert panel and community advisory board; (ii) conducting focus groups with experienced research participants; and (iii) theater testing a new curriculum in the target population. Key findings of this process indicate the importance of sophisticated community engagement strategies to shape research design and program implementation. Findings may be used to inform processes for future adaptation work, especially in sexual health programs for young Black girls and their mothers.

Heights and weights of Da-an boys: did sisters really make a difference?

This study further examined the negative association between boys' growth and the presence of sisters within a relatively affluent community in Taipei, Taiwan. Among 596 boys born in 1976-77, differences in height and log-transformed weight were judged using analysis of covariance (ANCOVA) with measurement age as a covariate, and parental education level (four levels), number of sisters (0, 1, 2 or 3+) and number of brothers (0, 1, 2+) as predictors. The relative importance of birth order and sibling sex was examined among the near majority of boys with one sibling (47%, 278/596). The sibling composition variable was defined using mutually exclusive categories representing individuals with one sibling: either one older or younger brother or sister. All boys contributed information before leaving middle school at a mean age of 14.9 +/- 0.4 years SD. The results were compared with similar analyses of data for 154 of these same boys for whom measurements were available from primary school entry at a mean age of 64 +/- 0.3 years SD onward. Results were also compared with data for a cohort of 153 boys who entered primary school later in 1986. Results confirm that boys from the Da-an area born in the mid-1970s who did not have sisters were significantly taller (2.2-2.5 cm, p < or = 0.008) and heavier (3.0-3.9 kg, p < or = 0.016) than those with one or two sisters. However, the 26 boys with three or more sisters, most of whom were last-born, were somewhat taller than those with one or two sisters. The same curvilinear relationships in height and weight appeared both among boys as they prepared to leave middle school and among the subset also measured just after entering primary school. When numbers of sisters were statistically controlled, the presence of two or more brothers was also significantly negatively associated with mean stature, but not weight, among middle school boys. Analyses among boys with one sibling revealed that birth order was associated with mean stature, but only if the sibling was female; an older sister was associated with a greater deficit in mean stature than a younger sister. Evidence of rising educational expectations, continued declines in family size with fewer gender-related differences in numbers of siblings, and a clear secular increase in body size in this community among children entering primary school from 1982 to 1986 suggest a possible explanatory model.

Aicardi-Goutières syndrome may present with positive newborn screen for X-linked adrenoleukodystrophy

We report three unrelated probands, two male and one female, diagnosed with Aicardi-Goutières syndrome (AGS) after screening positive on California newborn screening (CA NBS) for X-linked adrenoleukodystrophy (X-ALD) due to elevated C26:0 lysophosphatidylcholine (C26:0-LPC). Follow-up evaluation was notable for elevated C26:0, C26:1, and C26:0/C22:0 ratio, and normal red blood cell plasmalogens levels in all three probands. Diagnoses were confirmed by molecular sequencing prior to 12 months of age after clinical evaluation was inconsistent with X-ALD or suggestive of AGS. For at least one proband, the early diagnosis of AGS enabled candidacy for enrollment into a therapeutic clinical trial. This report demonstrates the importance of including AGS on the differential diagnosis for individuals who screen positive for X-ALD, particularly infants with abnormal neurological features, as this age of onset would be highly unusual for X-ALD. While AGS is not included on the Recommended Universal Screening Panel, affected individuals can be identified early through state NBS programs so long as providers are aware of a broader differential that includes AGS. This report is timely, as state NBS algorithms for X-ALD are actively being established, implemented, and refined.

Factors influencing diurnal variation in height among adults

This study evaluates height loss during the day in light of variables assessable through participant self-report. Participants were 19 female and 15 male staff and students who met with us twice with a mean interval between measurement sessions of 6.96h (SD=0.86). Hypotheses were evaluated using two-stage least squares regression analysis (SYSTAT 10). Males and females lost similar amounts of height between sessions (male,x¯=6.9mm;female,x¯=7.4mm). Among factors considered to impact overall height loss, sleep duration (Adj. R²=0.181, p=0.022) and height (Adj. R²=0.121, p=0.048) were useful in univariate analyses, though they were not significant in any models that included variables other than sex. Judging from log-transformed BMI variation, heavier males and females lost more height (F_{(2, 31)}=4.59, Adj. R²=0.179, p=0.018). Among factors anticipated to reduce height loss by acting prior to morning measurements, only time spent walking was significantly associated (β=2.6±0.8mm, t=3.16, p=0.004) when included as a predictor along with sex (p=0.17) and log-BMI (p=0.003). This model explained about 38% of height loss variance. None of the factors considered as potentially acting between measurement sessions showed statistically significant influences when included in the model just described, though predictor coefficients were in the anticipated direction. Results suggest that self-reported activities may be an important supplement to anthropometric studies, both for planning and later evaluation, particularly in large studies.

Multi-site validation of a functional assay to adjudicate SCN5A Brugada Syndrome-associated variants

Brugada Syndrome (BrS) is an inheritable arrhythmia condition that is associated with rare, loss-of-function variants in the cardiac sodium channel gene, SCN5A. Interpreting the pathogenicity of SCN5A missense variants is challenging and ~79% of SCN5A missense variants in ClinVar are currently classified as Variants of Uncertain Significance (VUS). An in vitro SCN5A-BrS automated patch clamp assay was generated for high-throughput functional studies of NaV1.5. The assay was independently studied at two separate research sites - Vanderbilt University Medical Center and Victor Chang Cardiac Research Institute - revealing strong correlations, including peak INa density (R2=0.86). The assay was calibrated according to ClinGen Sequence Variant Interpretation recommendations using high-confidence variant controls (n=49). Normal and abnormal ranges of function were established based on the distribution of benign variant assay results. The assay accurately distinguished benign controls (24/25) from pathogenic controls (23/24). Odds of Pathogenicity values derived from the experimental results yielded 0.042 for normal function (BS3 criterion) and 24.0 for abnormal function (PS3 criterion), resulting in up to strong evidence for both ACMG criteria. The calibrated assay was then used to study SCN5A VUS observed in four families with BrS and other arrhythmia phenotypes associated with SCN5A loss-of-function. The assay revealed loss-of-function for three of four variants, enabling reclassification to likely pathogenic. This validated APC assay provides clinical-grade functional evidence for the reclassification of current VUS and will aid future SCN5A-BrS variant classification.

The influence of variation in parental height dimorphism on same-sex parent-offspring height differences

OBJECTIVE

This study evaluates how adjusting for parental height dimorphism influences height differences among parents and same-sex offspring distinguished by parents' early backgrounds.

PARTICIPANTS AND METHODS

Regression analyses using data from independent groups of Taiwanese families, 56 with sons and 51 with daughters, evaluate how adjusting for parental height dimorphism influences same-sex parent-offspring height differences among families grouped by grandfathers' occupations into three status categories reflecting good to relatively poor early parental environments.

RESULTS

Parental height dimorphism was statistically significantly associated with same-sex parent-offspring height differences (father-son: mean Δ = 3.88 cm, β = -71.47 ± 11.49 SE, t = -6.22, p ≤ .0005; mother-daughter: mean Δ = 4.15 cm, β = 80.46 ± 18.52 SE, t = 4.35, p ≤ .0005). Adjusted mean father-son differences increased significantly across grandfathers' occupation categories (Privileged, Δ = 0.60, Business, Δ = 4.06, Farming & Labor, Δ = 5.28; p = .011). Mother-daughter differences were substantial, from 3.33 cm to 5.06 cm, but did not differ significantly across occupational categories (p = .63).

DISCUSSION

Adjustments here for variation in parent height dimorphism did not alter original interpretations that while female growth may be more canalized, it is similarly capable of responding to improvements in developmental contexts. Patterns of same-sex parent-offspring height differences across grandfathers' occupational categories remain best accounted for by Taiwan's rapidly expanding economy, substantial income equity and reductions in biases favoring sons over daughters. Adjustment for sub-group variation in parental height dimorphism should be considered in similar studies in the future.

Exploring the feasibility of using long-term stored newborn dried blood spots to identify metabolic features for congenital heart disease screening

Congenital heart disease (CHD) represents a significant contributor to both morbidity and mortality in neonates and children. There's currently no analogous dried blood spot (DBS) screening for CHD immediately after birth. This study was set to assess the feasibility of using DBS to identify reliable metabolite biomarkers with clinical relevance, with the aim to screen and classify CHD utilizing the DBS. We assembled a cohort of DBS datasets from the California Department of Public Health (CDPH) Biobank, encompassing both normal controls and three pre-defined CHD categories. A DBS-based quantitative metabolomics method was developed using liquid chromatography with tandem mass spectrometry (LC-MS/MS). We conducted a correlation analysis comparing the absolute quantitated metabolite concentration in DBS against the CDPH NBS records to verify the reliability of metabolic profiling. For hydrophilic and hydrophobic metabolites, we executed significant pathway and metabolite analyses respectively. Logistic and LightGBM models were established to aid in CHD discrimination and classification. Consistent and reliable quantification of metabolites were demonstrated in DBS samples stored for up to 15 years. We discerned dysregulated metabolic pathways in CHD patients, including deviations in lipid and energy metabolism, as well as oxidative stress pathways. Furthermore, we identified three metabolites and twelve metabolites as potential biomarkers for CHD assessment and subtypes classifying. This study is the first to confirm the feasibility of validating metabolite profiling results using long-term stored DBS samples. Our findings highlight the potential clinical applications of our DBS-based methods for CHD screening and subtype classification.

Multisite Validation of a Functional Assay to Adjudicate SCN5A Brugada Syndrome-Associated Variants

BACKGROUND

Brugada syndrome is an inheritable arrhythmia condition that is associated with rare, loss-of-function variants in SCN5A. Interpreting the pathogenicity of SCN5A missense variants is challenging, and ≈79% of SCN5A missense variants in ClinVar are currently classified as variants of uncertain significance. Automated patch clamp technology enables high-throughput functional studies of ion channel variants and can provide evidence for variant reclassification.

METHODS

An in vitro SCN5A-Brugada syndrome automated patch clamp assay was independently performed at Vanderbilt University Medical Center and Victor Chang Cardiac Research Institute. The assay was calibrated according to ClinGen Sequence Variant Interpretation recommendations using high-confidence variant controls (n=49). Normal and abnormal ranges of function were established based on the distribution of benign variant assay results. Odds of pathogenicity values were derived from the experimental results according to ClinGen Sequence Variant Interpretation recommendations. The calibrated assay was then used to study SCN5A variants of uncertain significance observed in 4 families with Brugada syndrome and other arrhythmia phenotypes associated with SCN5A loss-of-function.

RESULTS

Variant channel parameters generated independently at the 2 research sites showed strong correlations, including peak INa density (R2=0.86). The assay accurately distinguished benign controls (24/25 concordant variants) from pathogenic controls (23/24 concordant variants). Odds of pathogenicity values were 0.042 for normal function and 24.0 for abnormal function, corresponding to strong evidence for both American College of Medical Genetics and Genomics/Association for Molecular Pathology benign and pathogenic functional criteria (BS3 and PS3, respectively). Application of the assay to 4 clinical SCN5A variants of uncertain significance revealed loss-of-function for 3/4 variants, enabling reclassification to likely pathogenic.

CONCLUSIONS

This validated high-throughput assay provides clinical-grade functional evidence to aid the classification of current and future SCN5A-Brugada syndrome variants of uncertain significance.