Identification of putative pathogenic single nucleotide variants (SNVs) in genes associated with heart disease in 290 cases of stillbirth

Further exploration of cardiac channelopathy and cardiomyopathy genes in stillbirth

OBJECTIVE

To explore genetic variation including whole genome copy number variation and sequence analysis of 98 genes associated with pediatric or adult cardiomyopathies, cardiac channelopathies, and sudden death in an unexplained intrauterine fetal death cohort.

METHODS

The study population included 55 stillbirth cases that remained unexplained after thorough postmortem examination, excluding maternal, fetal, and placental causes of stillbirth. Molecular karyotyping was performed in 55 cases and the trio exome sequencing approach was applied in 19 cases.

RESULTS

The analysis revealed six rare variants with predicted effects on protein function in six genes (CASQ2, DSC2, KCNE1, LDB3, MYH6, and SCN5A) previously reported in cases of stillbirth or severe early onset pediatric cardiac related phenotypes. When applying strict American College of Genetics and Genomics classification guidelines, these are still variants of uncertain significance.

CONCLUSIONS

Several potentially stillbirth-related genetic variants were detected in our cohort, adding to the growing literature on cardiac phenotype gene variation in stillbirth. However, the mechanisms of action, gene-gene interaction, and contribution of the uterine environment are still to be deciphered. In order to advance our knowledge of the genetics of unexplained fetal death, there is an evident need for international collaboration and field standardization.

Structure, Function, and Regulation of the Junctophilin Family

In both excitable and nonexcitable cells, diverse physiological processes are linked to different calcium microdomains within nanoscale junctions that form between the plasma membrane and endo-sarcoplasmic reticula. It is now appreciated that the junctophilin protein family is responsible for establishing, maintaining, and modulating the structure and function of these junctions. We review foundational findings from more than two decades of research that have uncovered how junctophilin-organized ultrastructural domains regulate evolutionarily conserved biological processes. We discuss what is known about the junctophilin family of proteins. Our goal is to summarize the current knowledge of junctophilin domain structure, function, and regulation and to highlight emerging avenues of research that help our understanding of the transcriptional, translational, and post-translational regulation of this gene family and its roles in health and during disease.

Genomics of stillbirth

Stillbirth, defined as fetal death at 20 weeks gestation or later, is a devastating pregnancy outcome affecting 1 in 175 pregnancies in the United States. Although efforts to understand the etiology of stillbirth have expanded, 25 % of cases remain unexplained and some cases previously thought to be explained may have additional unknown causative factors. Determining an etiology for stillbirth is important for clinical management and for grieving families to obtain closure, to find meaning, and to understand recurrence risks. However, the evaluation of stillbirth is not completed uniformly despite American College of Obstetrics and Gynecology (ACOG) guidelines and stillbirth data is frequently incomplete due to lack of genomic analysis, fetal autopsy, and placental pathology. Karyotype and chromosomal microarray have been the gold standard in genetic analysis in perinatal medicine for many years, but next generation sequencing holds promise towards improving diagnostic yields and providing clarity for both clinicians and patients.

The Landscape of Point Mutations in Human Protein Coding Genes Leading to Pregnancy Loss

Pregnancy loss is the most frequent complication of a pregnancy which is devastating for affected families and poses a significant challenge for the health care system. Genetic factors are known to play an important role in the etiology of pregnancy loss; however, despite advances in diagnostics, the causes remain unexplained in more than 30% of cases. In this review, we aggregated the results of the decade-long studies into the genetic risk factors of pregnancy loss (including miscarriage, termination for fetal abnormality, and recurrent pregnancy loss) in euploid pregnancies, focusing on the spectrum of point mutations associated with these conditions. We reviewed the evolution of molecular genetics methods used for the genetic research into causes of pregnancy loss, and collected information about 270 individual genetic variants in 196 unique genes reported as genetic cause of pregnancy loss. Among these, variants in 18 genes have been reported by multiple studies, and two or more variants were reported as causing pregnancy loss for 57 genes. Further analysis of the properties of all known pregnancy loss genes showed that they correspond to broadly expressed, highly evolutionary conserved genes involved in crucial cell differentiation and developmental processes and related signaling pathways. Given the features of known genes, we made an effort to construct a list of candidate genes, variants in which may be expected to contribute to pregnancy loss. We believe that our results may be useful for prediction of pregnancy loss risk in couples, as well as for further investigation and revealing genetic etiology of pregnancy loss.

CEP55-associated lethal fetal syndrome: a case report of a Chinese family

Background: Research on fetal loss related to germline mutations in single genes remains limited. Disruption of CEP55 has recently been established in association with perinatal deaths characterized by hydranencephaly, renal dysplasia, oligohydramnios, and characteristic dysmorphisms. We herein present a Chinese family with recurrent fetal losses due to compound heterozygous nonsense CEP55 variants. Case presentations: The Chinese couple had a history of five pregnancies, with four of them proceeding abnormally. Two stillbirths (II:3 and II:4) sequentially occurred in the third and fourth pregnancy. Prenatal ultrasound scans revealed phenotypic similarities between fetuses II:3 and II:4, including oligohydramnios, bilateral renal dysplasia and hydrocephalus/hydranencephaly. Clubfoot and syndactyly were also present in both stillborn babies. Fetus II:3 presented with endocardial cushion defects while fetus II:4 did not. With the product of conception in the fourth pregnancy, whole exome sequencing (WES) on fetus II:4 identified compound heterozygous nonsense CEP55 variants comprised of c.190C>T(p.Arg64*) and c.208A>T(p.Lys70*). Both variants were expected to result in lack of the TSG101 and ALIX binding domain. Sanger sequencing confirmed the presence and cosegregation of both variants. Conclusion: This is the fifth reported family wherein biallelic CEP55 variants lead to multiple perinatal deaths. Our findings, taken together with previously described phenotypically similar cases and even those with a milder and viable phenotype, broaden the genotypic and phenotypic spectrum of CEP55-associated lethal fetal syndrome, highlighting the vital biomolecular function of CEP55.

The genetic approach to stillbirth: A »systematic review«

Unexplained stillbirth is defined as a stillbirth with no known cause after the exclusion of common causes, including obstetric complications, infections, placental insufficiency or abruption, umbilical cord complications, and congenital abnormalities with or without known genetic cause. More than 60% of stillbirth cases remain unexplained. The aim of this systematic review was to investigate the known genetic causes of unexplained stillbirth cases and to evaluate the current position and future directions for the use of genetic and genomic testing in expanding the knowledge in this field. A systematic search through several databases was performed using the keywords genetics and stillbirths in humans. Different methods to detect various types of causal genetic aberrations have been used in the past decades, from standard karyotyping to novel methods such as chromosomal microarray analysis and next generation sequencing technologies. Apart from common chromosomal aneuploidies, a promising hypothesis about genetic causes included genes related to cardiomyopathies and channelopathies. However, these were tested in the research settings, since molecular karyotyping is currently the standard approach in the routine evaluation of genetic causes of stillbirth. Hereby, we provide evidence that expanding knowledge using novel genetic and genomic testing might uncover new genetic causes of unexplained stillbirth.

Homozygous TNNI3 Mutations and Severe Early Onset Dilated Cardiomyopathy: Patient Report and Review of the Literature

The TNNI3 gene encodes for the cardiac isoform of troponin I, a pivotal component of the sarcomeric structure of the myocardium. While heterozygous TNNI3 missense mutations have long been associated with autosomal dominant hypertrophic and restrictive cardiomyopathies, the role of TNNI3 null mutations has been more debated due to the paucity and weak characterization of reported cases and the low penetrance of heterozygous genotypes. In recent years, however, an increasing amount of evidence has validated the hypothesis that biallelic TNNI3 null mutations cause a severe form of neonatal dilated cardiomyopathy. Here, we expand the case series reporting two unrelated patients afflicted with early onset dilated cardiomyopathy, due to homozygosity for the p.Arg98* TNNI3 variant, which had thus far been documented only in heterozygous patients and apparently healthy carriers, and the recurrent p.Arg69Alafs*8 variant, respectively. A review of previously reported biallelic TNNI3 loss-of-function variants and their associated cardiac phenotypes was also performed.

The chaperone-assisted selective autophagy complex dynamics and dysfunctions

Each protein must be synthesized with the correct amino acid sequence, folded into its native structure, and transported to a relevant subcellular location and protein complex. If any of these steps fail, the cell has the capacity to break down aberrant proteins to maintain protein homeostasis (also called proteostasis). All cells possess a set of well-characterized protein quality control systems to minimize protein misfolding and the damage it might cause. Autophagy, a conserved pathway for the degradation of long-lived proteins, aggregates, and damaged organelles, was initially characterized as a bulk degradation pathway. However, it is now clear that autophagy also contributes to intracellular homeostasis by selectively degrading cargo material. One of the pathways involved in the selective removal of damaged and misfolded proteins is chaperone-assisted selective autophagy (CASA). The CASA complex is composed of three main proteins (HSPA, HSPB8 and BAG3), essential to maintain protein homeostasis in muscle and neuronal cells. A failure in the CASA complex, caused by mutations in the respective coding genes, can lead to (cardio)myopathies and neurodegenerative diseases. Here, we summarize our current understanding of the CASA complex and its dynamics. We also briefly discuss how CASA complex proteins are involved in disease and may represent an interesting therapeutic target.Abbreviation ALP: autophagy lysosomal pathway; ALS: amyotrophic lateral sclerosis; AMOTL1: angiomotin like 1; ARP2/3: actin related protein 2/3; BAG: BAG cochaperone; BAG3: BAG cochaperone 3; CASA: chaperone-assisted selective autophagy; CMA: chaperone-mediated autophagy; DNAJ/HSP40: DnaJ heat shock protein family (Hsp40); DRiPs: defective ribosomal products; EIF2A/eIF2α: eukaryotic translation initiation factor 2A; EIF2AK1/HRI: eukaryotic translation initiation factor 2 alpha kinase 1; GABARAP: GABA type A receptor-associated protein; HDAC6: histone deacetylase 6; HSP: heat shock protein; HSPA/HSP70: heat shock protein family A (Hsp70); HSP90: heat shock protein 90; HSPB8: heat shock protein family B (small) member 8; IPV: isoleucine-proline-valine; ISR: integrated stress response; KEAP1: kelch like ECH associated protein 1; LAMP2A: lysosomal associated membrane protein 2A; LATS1: large tumor suppressor kinase 1; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOC: microtubule organizing center; MTOR: mechanistic target of rapamycin kinase; NFKB/NF-κB: nuclear factor kappa B; NFE2L2: NFE2 like bZIP transcription factor 2; PLCG/PLCγ: phospholipase C gamma; polyQ: polyglutamine; PQC: protein quality control; PxxP: proline-rich; RAN translation: repeat-associated non-AUG translation; SG: stress granule; SOD1: superoxide dismutase 1; SQSTM1/p62: sequestosome 1; STUB1/CHIP: STIP1 homology and U-box containing protein 1; STK: serine/threonine kinase; SYNPO: synaptopodin; TBP: TATA-box binding protein; TARDBP/TDP-43: TAR DNA binding protein; TFEB: transcription factor EB; TPR: tetratricopeptide repeats; TSC1: TSC complex subunit 1; UBA: ubiquitin associated; UPS: ubiquitin-proteasome system; WW: tryptophan-tryptophan; WWTR1: WW domain containing transcription regulator 1; YAP1: Yes1 associated transcriptional regulator.

Cardiac ion channels associated with unexplained stillbirth - an immunohistochemical study

OBJECTIVES

Despite the use of post-mortem investigations, approximately 20% of stillbirths remain unexplained. Cardiac ion channelopathies have been identified as a cause of death in Sudden Infant Death Syndrome (SIDS) and could be associated with unexplained stillbirths. This study aimed to understand if the expression or localisation of cardiac ion channels associated with channelopathies were altered in cases of unexplained stillbirths.

METHODS

A case control study was conducted using formalin-fixed cardiac tissue from 20 cases of unexplained stillbirth and a control group of 20 cases of stillbirths from intrapartum hypoxia. 4 µm tissue sections were stained using haematoxylin and eosin, Masson's trichrome (MT) and Elastic van Gieson (EVG). Immunohistochemistry (IHC) was performed using antibodies against CACNA1G, KCNJ2, KCNQ1, KCNH2 and KCNE1. The cardiac conduction system in samples stained with MT and EVG could not be identified. Therefore, the levels of immunoperoxidase staining were quantified using QuPath software.

RESULTS

The nuclear-cytoplasmic ratio of sections stained with haematoxylin and eosin was higher for the hypoxia group (hypoxia median 0.13 vs. 0.04 unexplained, p < 0.001). CACNA1G (unexplained median 0.26 vs. hypoxia 0.30, p=0.009) and KCNJ2 (unexplained median 0.35 vs. hypoxia 0.41, p=0.001) had lower staining intensity in the unexplained stillbirth group. There were no statistically significant differences in the staining intensity of KCNQ1, KCNH2 and KCNE1.

CONCLUSIONS

Two ion channels associated with channelopathies demonstrated lower levels of expression in cases of unexplained stillbirth. Further genetic studies using human tissue should be performed to understand the association between channelopathies and otherwise unexplained stillbirths.

Determinants of trafficking, conduction, and disease within a K+ channel revealed through multiparametric deep mutational scanning

A long-standing goal in protein science and clinical genetics is to develop quantitative models of sequence, structure, and function relationships to understand how mutations cause disease. Deep mutational scanning (DMS) is a promising strategy to map how amino acids contribute to protein structure and function and to advance clinical variant interpretation. Here, we introduce 7429 single-residue missense mutations into the inward rectifier K⁺ channel Kir2.1 and determine how this affects folding, assembly, and trafficking, as well as regulation by allosteric ligands and ion conduction. Our data provide high-resolution information on a cotranslationally folded biogenic unit, trafficking and quality control signals, and segregated roles of different structural elements in fold stability and function. We show that Kir2.1 surface trafficking mutants are underrepresented in variant effect databases, which has implications for clinical practice. By comparing fitness scores with expert-reviewed variant effects, we can predict the pathogenicity of 'variants of unknown significance' and disease mechanisms of known pathogenic mutations. Our study in Kir2.1 provides a blueprint for how multiparametric DMS can help us understand the mechanistic basis of genetic disorders and the structure-function relationships of proteins.

The role of BAG3 in health and disease: A "Magic BAG of Tricks"

The multi-domain structure of Bcl-2-associated athanogene 3 (BAG3) facilitates its interaction with many different proteins that participate in regulating a variety of biological pathways. After revisiting the BAG3 literature published over the past ten years with Citespace software, we classified the BAG3 research into several clusters, including cancer, cardiomyopathy, neurodegeneration, and viral propagation. We then highlighted recent key findings in each cluster. To gain greater insight into the roles of BAG3, we analyzed five different published mass spectrometry data sets of proteins that co-immunoprecipitate with BAG3. These data gave us insight into universal, as well as cell-type-specific BAG3 interactors in cancer cells, cardiomyocytes, and neurons. Finally, we mapped variable BAG3 SNPs and also mutation data from previous publications to further explore the link between the domains and function of BAG3. We believe this review will provide a better understanding of BAG3 and direct future studies towards understanding BAG3 function in physiological and pathological conditions.

Pitfalls of International Classification of Diseases - Perinatal mortality in analysing stillbirths

OBJECTIVES

This study aimed to evaluate the trend of stillbirth from 2009 to 2018. The causes of stillbirth were classified using the International Classification of Diseases - Perinatal Mortality (ICD-PM).

STUDY DESIGN AND METHODS

A retrospective chart review was performed on 135 stillbirths from 2009 to 2018 in a tertiary university teaching hospital. The annual stillbirth rate was calculated, and the trend was evaluated. The cause of death was reclassified using ICD-PM.

RESULTS

The stillbirth rate was 3.70 per 1000 total births, and it remained stable over the studied period (P = 0.238). Most of the stillbirth (97.8%) were antepartum deaths. The proportion of unexplained stillbirth was reduced from 57% to 18.5% after reclassified by ICD-PM coding. Another major cause of antepartum stillbirths was disorders related to fetal growth, which consisted of mothers with medical and surgical conditions (11%, n = 15, ICD-PM code A5, M4) or mothers with complications of placenta, cord and membranes (8.9%, n = 12, ICD-PM code A5, M1).

CONCLUSION

The use of ICD-PM was useful in reducing the proportion of unexplained stillbirths. ICD-PM has the advantages of coding related to the timing of stillbirth and associated maternal conditions. Pitfalls including the unclear use of the code A3-'antepartum hypoxia,' guidance on coding of well-controlled maternal medical conditions and placental pathology and the importance of subcategorisation need to be addressed.

Molecular autopsy by proxy in preconception counseling

Monogenic diseases that result in early pregnancy loss or neonatal death are genetically and phenotypically highly variable. This often poses significant challenges in arriving at a molecular diagnosis for reproductive planning. Molecular autopsy by proxy (MABP) refers to the genetic testing of relatives of deceased individuals to deduce the cause of death. Here, we specifically tested couples who lost one or more children/pregnancies with no available DNA. We developed our testing strategy using whole exome sequencing data from 83 consanguineous Saudi couples. We detected the shared carrier state of 50 pathogenic variants/likely pathogenic variants in 43 families and of 28 variants of uncertain significance in 24 families. Negative results were seen in 16 couples after variant reclassification. In 10 families, the risk of more than one genetic disease was documented. Secondary findings were seen in 10 families: either genetic variants with potential clinical consequences for the tested individual or a female carrier for X‐linked conditions. This couple‐based approach has enabled molecularly informed genetic counseling for 52% (43/83 families). Given the predominance of autosomal recessive causes of pregnancy and child death in consanguineous populations, MABP can be a helpful approach to consanguineous couples who seek counseling but lack molecular data on their deceased offspring.

Recurrent Pregnancy Loss and Concealed Long-QT Syndrome

Background

Recurrent pregnancy loss affects 1% to 2% of couples attempting childbirth. A large fraction of all cases remains idiopathic, which warrants research into monogenic causes of this distressing disorder.

Methods and Results

We investigated a nonconsanguineous Estonian family who had experienced 5 live births, intersected by 3 early pregnancy losses, and 6 fetal deaths, 3 of which occurred during the second trimester. No fetal malformations were described at the autopsies performed in 3 of 6 cases of fetal death. Parental and fetal chromosomal abnormalities (including submicroscopic) and maternal risk factors were excluded. Material for genetic testing was available from 4 miscarried cases (gestational weeks 11, 14, 17, and 18). Exome sequencing in 3 pregnancy losses and the mother identified no rare variants explicitly shared by the miscarried conceptuses. However, the mother and 2 pregnancy losses carried a heterozygous nonsynonymous variant, resulting in p.Val173Asp (rs199472695) in the ion channel gene KCNQ1. It is expressed not only in heart, where mutations cause type 1 long‐QT syndrome, but also in other tissues, including uterus. The p.Val173Asp variant has been previously identified in a patient with type 1 long‐QT syndrome, but not reported in the Genome Aggregation Database. With heterologous expression in CHO cells, our in vitro electrophysiologic studies indicated that the mutant slowly activating voltage‐gated K+ channel (I_Ks) is dysfunctional. It showed reduced total activating and deactivating currents (P<0.01), with dramatically positive shift of voltage dependence of activation by ≈10 mV (P<0.05).

Conclusions

The current study uncovered concealed maternal type 1 long‐QT syndrome as a potential novel cause behind recurrent fetal loss.

Cardio-pathogenic variants in unexplained intrauterine fetal death: a retrospective pilot study

To describe the prevalence and spectrum of cardio-pathogenic variants in singleton fetuses after unexplained intrauterine fetal death (IUFD). DNA from post-mortem fibroblastic tissue samples of 16 fetuses after unexplained IUFD was retrieved at two tertiary university hospitals for clinical exome sequencing with subsequent filtering of 122 cardio-specific genes to elucidate underlying cardio-pathogenic variants. In total, we included 12 (75%) male and four (25%) female fetuses who were stillborn at a median gestational age of 34⁺⁶ (23⁺²–40⁺⁵) weeks. In two (12.5%) fetuses no cardio-pathogenic variants were found. In 14 (87.5%) fetuses, overall 33 variants were detected in 22 cardio-specific genes, involving 14 (63.63%) genes associated with cardiomyopathy, six (27.27%) arrhythmogenic susceptibility genes and two (9.09%) arrhythmia and cardiomyopathy associated genes. Among the 33 variants, five (15.2%) were classified as likely benign according to the American College of Medical Genetics and Genomics; 28 (84.8%) variants were considered as variants of uncertain significance. Compared to a cohort of explained IUFDs, the cases with and without fetal variants in cardiac genes differed not significantly regarding maternal age, previous history of stillbirth, time of stillbirth or fetal sex. Unexplained stillbirth may be caused by cardio-genetic pathologies, yet a high number of variants of uncertain significance merit a more detailed post-mortem examination including family segregation analysis.

Causal Genetic Variants in Stillbirth

BACKGROUND

In the majority of cases, the cause of stillbirth remains unknown despite detailed clinical and laboratory evaluation. Approximately 10 to 20% of stillbirths are attributed to chromosomal abnormalities. However, the causal nature of single-nucleotide variants and small insertions and deletions in exomes has been understudied.

METHODS

We generated exome sequencing data for 246 stillborn cases and followed established guidelines to identify causal variants in disease-associated genes. These genes included those that have been associated with stillbirth and strong candidate genes. We also evaluated the contribution of 18,653 genes in case-control analyses stratified according to the degree of depletion of functional variation (described here as "intolerance" to variation).

RESULTS

We identified molecular diagnoses in 15 of 246 cases of stillbirth (6.1%) involving seven genes that have been implicated in stillbirth and six disease genes that are good candidates for phenotypic expansion. Among the cases we evaluated, we also found an enrichment of loss-of-function variants in genes that are intolerant to such variation in the human population (odds ratio, 2.15; 95% confidence interval [CI], 1.46 to 3.06). Loss-of-function variants in intolerant genes were concentrated in genes that have not been associated with human disease (odds ratio, 2.22; 95% CI, 1.41 to 3.34), findings that differ from those in two postnatal clinical populations that were also evaluated in this study.

CONCLUSIONS

Our findings establish the diagnostic utility of clinical exome sequencing to evaluate the role of small genomic changes in stillbirth. The strength of the novel risk signal (as generated through the stratified analysis) was similar to that in known disease genes, which indicates that the genetic cause of stillbirth remains largely unknown. (Funded by the Institute for Genomic Medicine.).

Fetal HLA-G mediated immune tolerance and interferon response in preeclampsia

BACKGROUND

Fetal immune tolerance is crucial for pregnancy success. We studied the link between preeclampsia, a severe pregnancy disorder with uncertain pathogenesis, and fetal human leukocyte antigen G (HLA-G) and other genes regulating maternal immune responses.

METHODS

We assessed sex ratios and regulatory HLA-G haplotypes in population cohorts and series of preeclampsia and stillbirth. We studied placental mRNA expression of 136 genes by sequencing and HLA-G and interferon alpha (IFNα) protein expression by immunohistochemistry.

FINDINGS

We found underrepresentation of males in preeclamptic births, especially those delivered preterm or small for gestational age. Balancing selection at HLA-G associated with the sex ratio, stillbirth, and preeclampsia. We observed downregulation of HLA-G, its receptors, and many other tolerogenic genes, and marked upregulation of IFNA1 in preeclamptic placentas.

INTERPRETATION

These findings indicate that an evolutionary trade-off between immune tolerance and protection against infections at the maternal-fetal interface promotes genetic diversity in fetal HLA-G, thereby affecting survival, preeclampsia, and sex ratio. We highlight IFNA1 as a potential mediator of preeclampsia and a target for therapeutic trials.

FUNDING

Finnish Medical Foundation, Päivikki and Sakari Sohlberg Foundation, Karolinska Institutet Research Foundation, Scandinavia-Japan Sasakawa Foundation, Japan Eye Bank Association, Astellas Foundation for Research on Metabolic Disorders, Japan Society for the Promotion of Science, Knut and Alice Wallenberg Foundation, Swedish Research Council, Medical Society Liv och Hälsa, Sigrid Jusélius Foundation, Helsinki University Hospital and University of Helsinki, Jane and Aatos Erkko Foundation, Academy of Finland, Finska Läkaresällskapet, Novo Nordisk Foundation, Finnish Foundation for Pediatric Research, and Emil Aaltonen Foundation.

Genetic innovations and our understanding of stillbirth

Stillbirth after 20 weeks gestation happens in 1 in 200 pregnancies and occurs more commonly than neonatal loss and sudden infant death syndrome (SIDs) combined. The stillbirth rate is several times greater in low as opposed to high-resource countries. However, among high-resource countries, although a lower overall stillbirth rate exists, there has been little change for several decades. Molecular genetic technologies are emerging as important contributors to our understanding of stillbirth. Initially, genetic etiologies included alterations in chromosome number or structure such as aneuploidy and microduplications and deletions. More recently, next-generation sequencing analysis in two genetic conditions, Smith Lemli Optiz Syndrome (SLOs) and the channelopathy disorders (such as long QT syndrome (LQTS)) provide examples into the association of pathogenic gene variants with stillbirth. Although these specific conditions individually account for only a small number of stillbirths, investigating these disorders provides a new and innovative approach for further understanding genetic contributors to adverse pregnancy outcomes. Our knowledge of the role of genetic disease as an etiology for stillbirth is elementary. Genomic interrogation of maternal-fetal genotypes, gene-gene, and genotype-environment interaction is lacking in stillbirth research. At the DNA sequence level, further investigation of variants of unknown significance is an opportunity for exploration of biologic pathways of importance to pregnancy loss. This review concentrates on SLO as an example of a single gene disorder with a high carrier but low affected liveborn proband rate. The channelopathy disorders are included as initial examples of genetic conditions with variable presentation including an association with sudden infant death syndrome. Highlighted are the challenges when numerous genes and variants are involved, and the task of assigning pathogenicity. The advantages and limitations of genetic evaluations are presented and avenues for further research considered.

Neuromuscular Diseases Due to Chaperone Mutations: A Review and Some New Results

Skeletal muscle and the nervous system depend on efficient protein quality control, and they express chaperones and cochaperones at high levels to maintain protein homeostasis. Mutations in many of these proteins cause neuromuscular diseases, myopathies, and hereditary motor and sensorimotor neuropathies. In this review, we cover mutations in DNAJB6, DNAJB2, αB-crystallin (CRYAB, HSPB5), HSPB1, HSPB3, HSPB8, and BAG3, and discuss the molecular mechanisms by which they cause neuromuscular disease. In addition, previously unpublished results are presented, showing downstream effects of BAG3 p.P209L on DNAJB6 turnover and localization.