Genome-wide analysis of copy-number variation in humans with cleft lip and/or cleft palate identifies COBLL1, RIC1, and ARHGEF38 as clefting genes.

Cleft lip with or without cleft palate (CL/P) is a common birth defect with a complex, heterogeneous etiology. It is well established that common and rare sequence variants contribute to the formation of CL/P, but the contribution of copy-number variants (CNVs) to cleft formation remains relatively understudied. To fill this knowledge gap, we conducted a large-scale comparative analysis of genome-wide CNV profiles of 869 individuals from the Philippines and 233 individuals of European ancestry with CL/P with three primary goals: first, to evaluate whether differences in CNV number, amount of genomic content, or amount of coding genomic content existed within clefting subtypes; second, to assess whether CNVs in our cohort overlapped with known Mendelian clefting loci; and third, to identify unestablished Mendelian clefting genes. Significant differences in CNVs across cleft types or in individuals with non-syndromic versus syndromic clefts were not observed; however, several CNVs in our cohort overlapped with known syndromic and non-syndromic Mendelian clefting loci. Moreover, employing a filtering strategy relying on population genetics data that rare variants are on the whole more deleterious than common variants, we identify several CNV-associated gene losses likely driving non-syndromic clefting phenotypes. By prioritizing genes deleted at a rare frequency across multiple individuals with clefts yet enriched in our cohort of individuals with clefts compared to control subjects, we identify COBLL1, RIC1, and ARHGEF38 as clefting genes. CRISPR-Cas9 mutagenesis of these genes in Xenopus laevis and Danio rerio yielded craniofacial dysmorphologies, including clefts analogous to those seen in human clefting disorders.

Mapping the Evolutionary Space of SARS-CoV-2 Variants to Anticipate Emergence of Subvariants Resistant to COVID-19 Therapeutics.

New sublineages of SARS-CoV-2 variants-of-concern (VOCs) continuously emerge with mutations in the spike glycoprotein. In most cases, the sublineage-defining mutations vary between the VOCs. It is unclear whether these differences reflect lineage-specific likelihoods for mutations at each spike position or the stochastic nature of their appearance. Here we show that SARS-CoV-2 lineages have distinct evolutionary spaces (a probabilistic definition of the sequence states that can be occupied by expanding virus subpopulations). This space can be accurately inferred from the patterns of amino acid variability at the whole-protein level. Robust networks of co-variable sites identify the highest-likelihood mutations in new VOC sublineages and predict remarkably well the emergence of subvariants with resistance mutations to COVID-19 therapeutics. Our studies reveal the contribution of low frequency variant patterns at heterologous sites across the protein to accurate prediction of the changes at each position of interest.

Sporadic hypothalamic hamartoma is a ciliopathy with somatic and bi-allelic contributions.

Hypothalamic hamartoma with gelastic seizures is a well-established cause of drug-resistant epilepsy in early life. The development of novel surgical techniques has permitted the genomic interrogation of hypothalamic hamartoma tissue. This has revealed causative mosaic variants within GLI3, OFD1 and other key regulators of the sonic-hedgehog pathway in a minority of cases. Sonic-hedgehog signalling proteins localize to the cellular organelle primary cilia. We therefore explored the hypothesis that cilia gene variants may underlie hitherto unsolved cases of sporadic hypothalamic hamartoma. We performed high-depth exome sequencing and chromosomal microarray on surgically resected hypothalamic hamartoma tissue and paired leukocyte-derived DNA from 27 patients. We searched for both germline and somatic variants under both dominant and bi-allelic genetic models. In hamartoma-derived DNA of seven patients we identified bi-allelic (one germline, one somatic) variants within one of four cilia genes-DYNC2I1, DYNC2H1, IFT140 or SMO. In eight patients, we identified single somatic variants in the previously established hypothalamic hamartoma disease genes GLI3 or OFD1. Overall, we established a plausible molecular cause for 15/27 (56%) patients. Here, we expand the genetic architecture beyond single variants within dominant disease genes that cause sporadic hypothalamic hamartoma to bi-allelic (one germline/one somatic) variants, implicate three novel cilia genes and reconceptualize the disorder as a ciliopathy.

The Influence of a Genetic Variant in CCDC78 on LMNA-Associated Skeletal Muscle Disease.

Mutations in the LMNA gene-encoding A-type lamins can cause Limb-Girdle muscular dystrophy Type 1B (LGMD1B). This disease presents with weakness and wasting of the proximal skeletal muscles and has a variable age of onset and disease severity. This variability has been attributed to genetic background differences among individuals; however, such variants have not been well characterized. To identify such variants, we investigated a multigeneration family in which affected individuals are diagnosed with LGMD1B. The primary genetic cause of LGMD1B in this family is a dominant mutation that activates a cryptic splice site, leading to a five-nucleotide deletion in the mature mRNA. This results in a frame shift and a premature stop in translation. Skeletal muscle biopsies from the family members showed dystrophic features of variable severity, with the muscle fibers of some family members possessing cores, regions of sarcomeric disruption, and a paucity of mitochondria, not commonly associated with LGMD1B. Using whole genome sequencing (WGS), we identified 21 DNA sequence variants that segregate with the family members possessing more profound dystrophic features and muscle cores. These include a relatively common variant in coiled-coil domain containing protein 78 (CCDC78). This variant was given priority because another mutation in CCDC78 causes autosomal dominant centronuclear myopathy-4, which causes cores in addition to centrally positioned nuclei. Therefore, we analyzed muscle biopsies from family members and discovered that those with both the LMNA mutation and the CCDC78 variant contain muscle cores that accumulated both CCDC78 and RyR1. Muscle cores containing mislocalized CCDC78 and RyR1 were absent in the less profoundly affected family members possessing only the LMNA mutation. Taken together, our findings suggest that a relatively common variant in CCDC78 can impart profound muscle pathology in combination with a LMNA mutation and accounts for variability in skeletal muscle disease phenotypes.

CRELD1 variants are associated with bicuspid aortic valve in Turner syndrome.

Turner syndrome (TS) is a chromosomal disorder caused by complete or partial loss of the second sex chromosome and exhibits phenotypic heterogeneity, even after accounting for mosaicism and karyotypic variation. Congenital heart defects (CHD) are found in up to 45 percent of girls with TS and span a phenotypic continuum of obstructive left-sided lesions, with bicuspid aortic valve (BAV) being the most common. Several recent studies have demonstrated a genome-wide impact of X chromosome haploinsufficiency, including global hypomethylation and altered RNA expression. The presence of such broad changes to the TS epigenome and transcriptome led others to hypothesize that X chromosome haploinsufficiency sensitizes the TS genome, and several studies have demonstrated that a second genetic hit can modify disease susceptibility in TS. The objective of this study was to determine whether genetic variants in known heart developmental pathways act synergistically in this setting to increase the risk for CHD, specifically BAV, in TS. We analyzed 208 whole exomes from girls and women with TS and performed gene-based variant enrichment analysis and rare-variant association testing to identify variants associated with BAV in TS. Notably, rare variants in CRELD1 were significantly enriched in individuals with TS who had BAV compared to those with structurally normal hearts. CRELD1 is a protein that functions as a regulator of calcineurin/NFAT signaling, and rare variants in CRELD1 have been associated with both syndromic and non-syndromic CHD. This observation supports the hypothesis that genetic modifiers outside the X chromosome that lie in known heart development pathways may influence CHD risk in TS.

Intron mutations and early transcription termination in Duchenne and Becker muscular dystrophy.

DMD pathogenic variants for Duchenne and Becker muscular dystrophy are detectable with high sensitivity by standard clinical exome analyses of genomic DNA. However, up to 7% of DMD mutations are deep intronic and analysis of muscle-derived RNA is an important diagnostic step for patients who have negative genomic testing but abnormal dystrophin expression in muscle. In this study, muscle biopsies were evaluated from 19 patients with clinical features of a dystrophinopathy, but negative clinical DMD mutation analysis. Reverse transcription-polymerase chain reaction or high-throughput RNA sequencing methods identified 19 mutations with one of three pathogenic pseudoexon types: deep intronic point mutations, deletions or insertions, and translocations. In association with point mutations creating intronic splice acceptor sites, we observed the first examples of DMD pseudo 3'-terminal exon mutations causing high efficiency transcription termination within introns. This connection between splicing and premature transcription termination is reminiscent of U1 snRNP-mediating telescripting in sustaining RNA polymerase II elongation across large genes, such as DMD. We propose a novel classification of three distinct types of mutations identifiable by muscle RNA analysis, each of which differ in potential treatment approaches. Recognition and appropriate characterization may lead to therapies directed toward full-length dystrophin expression for some patients.

Using an aquatic model, Xenopus laevis, to uncover the role of chromodomain 1 in craniofacial disorders.

The chromodomain family member chromodomain 1 (CHD1) has been shown to have numerous critical molecular functions including transcriptional regulation, splicing, and DNA repair. Complete loss of function of this gene is not compatible with life. On the other hand, missense and copy number variants of CHD1 can result in intellectual disabilities and craniofacial malformations in human patients including cleft palate and Pilarowski-Bjornsson Syndrome. We have used the aquatic developmental model organism Xenopus laevis, to determine a specific role for Chd1 in such cranioafcial disorders. Protein and gene knockdown techniques in Xenopus, including antisense oligos and mosaic Crispr/Cas9-mediated mutagenesis, recapitulated the craniofacial defects observed in humans. Further analysis indicated that embryos deficient in Chd1 had defects in cranial neural crest development and jaw cartilage morphology. Additionally, flow cytometry and immunohistochemistry revealed that decreased Chd1 resulted in increased in apoptosis in the developing head. Together, these experiments demonstrate that Chd1 is critical for fundamental processes and cell survival in craniofacial development. We also presented evidence that Chd1 is regulated by retinoic acid signaling during craniofacial development. Expression levels of chd1 mRNA, specifically in the head, were increased by RAR agonist exposure and decreased upon antagonist treatment. Subphenotypic levels of an RAR antagonist and Chd1 morpholinos synergized to result in orofacial defects. Further, RAR DNA binding sequences (RAREs) were detected in chd1 regulatory regions by bioinformatic analysis. In summary, by combining human genetics and experiments in an aquatic model we now have a better understanding of the role of CHD1 in craniofacial disorders.

Presacral neuroendocrine tumors associated with the Currarino syndrome.

Currarino syndrome (CS) is an autosomal dominant syndrome caused by mutations in MNX1 and characterized by anorectal abnormalities, partial sacral agenesis, and presacral masses. The presacral masses are typically benign; however, malignant degeneration can occur, and presacral neuroendocrine tumors (NETs) have been reported in six cases. We report three individuals from two families affected by CS in which multiple individuals developed presacral NETs. The first family, 491, had six members with features of CS, including two siblings who presented with presacral, Grade 2 NETs, one of which had metastasized to bone and lymph nodes. A germline c.874C>T (p.Arg292Trp) mutation was found in a highly conserved region of MNX1 in three affected members who underwent sequencing. A second somatic variant/deletion in MNX1 was not detected in either patient's tumor. In the second family, 342, the proband presented with an incidentally discovered presacral NET. The proband's father had previously undergone resection of a presacral NET, and so genetic testing was performed, which did not reveal an MNX1 mutation or copy number variants. The lack of a second, somatic mutation in the tumors from family 491 argues against MNX1 acting as a tumor suppressor, and the absence of a germline MNX1 mutation in family 342 suggests that other genetic and anatomic factors contribute to the development of presacral NETs. These cases highlight the variable presentation of CS, and the potential for malignancy in these patients.

Sequential genetic testing of living-related donors for inherited renal disease to promote informed choice and enhance safety of living donation.

Living kidney donors (LKDs) with a family history of renal disease are at risk of kidney disease as compared to LKDs without such history suggesting that some LKDs may be pre-symptomatic for monogenic kidney disease. LKDs with related transplant candidates whose kidney disease was considered genetic in origin were selected for genetic testing. In each case, the transplant candidate was first tested to verify the genetic diagnosis. A genetic diagnosis was confirmed in 12 of 24 transplant candidates (ADPKD-PKD1: 6, ALPORT-COL4A3: 2, ALPORT-COL4A5: 1: nephronophthisis-SDCCAG8: 1; CAKUT-HNF1B and ADTKD-MUC1: 1 each) and 2 had variants of unknown significance (VUS) in phenotype-relevant genes. Focused genetic testing was then done in 20 of 34 LKDs. 12 LKDs screened negative for the familial variant and were permitted to donate; seven screened positive and were counseled against donation. One, the heterozygous carrier of a recessive disorder was also cleared. Six of seven LKDs with a family history of ADPKD were under 30 years and in 5, by excluding ADPKD, allowed donation to safely proceed. The inclusion of genetic testing clarified the diagnosis in recipient candidates, improving safety or informed decision-making in LKDs.

Expanding the genotypic and phenotypic spectrum of severe serine biosynthesis disorders.

Serine biosynthesis disorders comprise a spectrum of very rare autosomal recessive inborn errors of metabolism with wide phenotypic variability. Neu-Laxova syndrome represents the most severe expression and is characterized by multiple congenital anomalies and pre- or perinatal lethality. Here, we present the mutation spectrum and a detailed phenotypic analysis in 15 unrelated families with severe types of serine biosynthesis disorders. We identified likely disease-causing variants in the PHGDH and PSAT1 genes, several of which have not been reported previously. Phenotype analysis and a comprehensive review of the literature corroborates the evidence that serine biosynthesis disorders represent a continuum with varying degrees of phenotypic expression and suggest that even gradual differences at the severe end of the spectrum may be correlated with particular genotypes. We postulate that the individual residual enzyme activity of mutant proteins is the major determinant of the phenotypic variability, but further functional studies are needed to explore effects at the enzyme protein level.

Mutations of the Sonic Hedgehog Pathway Underlie Hypothalamic Hamartoma with Gelastic Epilepsy.

Hypothalamic hamartoma (HH) with gelastic epilepsy is a well-recognized drug-resistant epilepsy syndrome of early life.(1) Surgical resection allows limited access to the small deep-seated lesions that cause the disease. Here, we report the results of a search for somatic mutations in paired hamartoma- and leukocyte-derived DNA samples from 38 individuals which we conducted by using whole-exome sequencing (WES), chromosomal microarray (CMA), and targeted resequencing (TRS) of candidate genes. Somatic mutations were identified in genes involving regulation of the sonic hedgehog (Shh) pathway in 14/38 individuals (37%). Three individuals had somatic mutations in PRKACA, which encodes a cAMP-dependent protein kinase that acts as a repressor protein in the Shh pathway, and four subjects had somatic mutations in GLI3, an Shh pathway gene associated with HH. In seven other individuals, we identified two recurrent and three single brain-tissue-specific, large copy-number or loss-of-heterozygosity (LOH) variants involving multiple Shh genes, as well as other genes without an obvious biological link to the Shh pathway. The Shh pathway genes in these large somatic lesions include the ligand itself (SHH and IHH), the receptor SMO, and several other Shh downstream pathway members, including CREBBP and GLI2. Taken together, our data implicate perturbation of the Shh pathway in at least 37% of individuals with the HH epilepsy syndrome, consistent with the concept of a developmental pathway brain disease.

In trans variant calling reveals enrichment for compound heterozygous variants in genes involved in neuronal development and growth.

Compound heterozygotes occur when different variants at the same locus on both maternal and paternal chromosomes produce a recessive trait. Here we present the tool VarCount for the quantification of variants at the individual level. We used VarCount to characterize compound heterozygous coding variants in patients with epileptic encephalopathy and in the 1000 Genomes Project participants. The Epi4k data contains variants identified by whole exome sequencing in patients with either Lennox-Gastaut Syndrome (LGS) or infantile spasms (IS), as well as their parents. We queried the Epi4k dataset (264 trios) and the phased 1000 Genomes Project data (2504 participants) for recessive variants. To assess enrichment, transcript counts were compared between the Epi4k and 1000 Genomes Project participants using minor allele frequency (MAF) cutoffs of 0.5 and 1.0%, and including all ancestries or only probands of European ancestry. In the Epi4k participants, we found enrichment for rare, compound heterozygous variants in six genes, including three involved in neuronal growth and development - PRTG (p = 0.00086, 1% MAF, combined ancestries), TNC (p = 0.022, 1% MAF, combined ancestries) and MACF1 (p = 0.0245, 0.5% MAF, EU ancestry). Due to the total number of transcripts considered in these analyses, the enrichment detected was not significant after correction for multiple testing and higher powered or prospective studies are necessary to validate the candidacy of these genes. However, PRTG, TNC and MACF1 are potential novel recessive epilepsy genes and our results highlight that compound heterozygous variants should be considered in sporadic epilepsy.

A case of primary cutaneous Ewing sarcoma in a neutropenic patient.

Primary cutaneous Ewing sarcoma is a rare clinical presentation of Ewing sarcoma, usually occurring as a small, localized tumor on the extremities of young adults and associated with favorable prognosis. We report a case of primary cutaneous Ewing sarcoma, which presented on the sole of the foot of a 27-year-old patient with relapsed acute myeloid leukemia and neutropenia. Diagnosis was determined through histological features and staining, as well as fluorescence in situ hybridization and molecular testing. The patient underwent wide-local excision with plan to begin targeted chemotherapy, but unfortunately died from adenovirus pneumonia while neutropenic before targeted chemotherapy was initiated.

A novel porcine model of ataxia telangiectasia reproduces neurological features and motor deficits of human disease.

Ataxia telangiectasia (AT) is a progressive multisystem disorder caused by mutations in the AT-mutated (ATM) gene. AT is a neurodegenerative disease primarily characterized by cerebellar degeneration in children leading to motor impairment. The disease progresses with other clinical manifestations including oculocutaneous telangiectasia, immune disorders, increased susceptibly to cancer and respiratory infections. Although genetic investigations and physiological models have established the linkage of ATM with AT onset, the mechanisms linking ATM to neurodegeneration remain undetermined, hindering therapeutic development. Several murine models of AT have been successfully generated showing some of the clinical manifestations of the disease, however they do not fully recapitulate the hallmark neurological phenotype, thus highlighting the need for a more suitable animal model. We engineered a novel porcine model of AT to better phenocopy the disease and bridge the gap between human and current animal models. The initial characterization of AT pigs revealed early cerebellar lesions including loss of Purkinje cells (PCs) and altered cytoarchitecture suggesting a developmental etiology for AT and could advocate for early therapies for AT patients. In addition, similar to patients, AT pigs show growth retardation and develop motor deficit phenotypes. By using the porcine system to model human AT, we established the first animal model showing PC loss and motor features of the human disease. The novel AT pig provides new opportunities to unmask functions and roles of ATM in AT disease and in physiological conditions.

Development of Secondary Acute Myeloid Leukemia in a Pediatric Patient Concurrently Receiving Primary Therapy for Ewing Sarcoma.

Ewing sarcoma is a pediatric bone and soft tissue sarcoma that requires intensive therapy, which can cause secondary malignancies. We present a rare case of early, treatment-related AML in a pediatric patient concurrently receiving primary therapy for Ewing sarcoma. Despite AML-directed therapy, our patient died secondary to complications of hyperleukocytosis. Cytogenetic and mutation profiling of the leukemia cells revealed the DNA-topoisomerase-II-inhibitor-associated t(9;11)(p22;q23) translocation and clonal KRAS and BRAF mutations. This report highlights the importance of monitoring for treatment-related effects in cancer therapy, as well as the need for novel, less toxic approaches in Ewing sarcoma therapy.

The heritability of hemolysis in stored human red blood cells.

BACKGROUND: The transfusion of red blood cells (RBCs) with maximum therapeutic efficacy is a major goal in transfusion medicine. One of the criteria used in determining stored RBC quality is end-of-storage hemolysis. Between donors, a wide range of hemolysis is observed under identical storage conditions. Here, a potential mechanism for this wide range is investigated. We hypothesize that the magnitude of hemolysis is a heritable trait. Also, we investigated correlations between hemolysis and RBC metabolites; this will establish pathways influencing hemolysis as future targets for genetic analysis. STUDY DESIGN AND METHODS: Units of RBCs from identical and nonidentical twins were collected and stored under standard conditions for 56 days. Hemolysis, adenosine triphosphate (ATP), and total glutathione (tGSH) were measured throughout storage. Nontargeted metabolic analyses were performed on RBCs that had been stored for 28 days. Heritability was determined by comparing values between identical and nonidentical twins. RESULTS: Hemolysis was found to be heritable (mean > 45%) throughout the storage period. Potential correlations were observed between hemolysis and metabolites from the purine metabolism, lysolipid, and glycolysis pathways. These also exhibited heritability (>20%). No correlation was found with ATP or tGSH. CONCLUSION: The susceptibility of RBCs to lysis during storage is partly determined by inheritance. We have also uncovered several pathways that are candidate targets for future genomewide association studies. These findings will aid in the design of better storage solutions and the development of donor screening tools that minimize hemolysis during storage.

CNV-ROC: A cost effective, computer-aided analytical performance evaluator of chromosomal microarrays.

Chromosomal microarrays (CMAs) are routinely used in both research and clinical laboratories; yet, little attention has been given to the estimation of genome-wide true and false negatives during the assessment of these assays and how such information could be used to calibrate various algorithmic metrics to improve performance. Low-throughput, locus-specific methods such as fluorescence in situ hybridization (FISH), quantitative PCR (qPCR), or multiplex ligation-dependent probe amplification (MLPA) preclude rigorous calibration of various metrics used by copy number variant (CNV) detection algorithms. To aid this task, we have established a comparative methodology, CNV-ROC, which is capable of performing a high throughput, low cost, analysis of CMAs that takes into consideration genome-wide true and false negatives. CNV-ROC uses a higher resolution microarray to confirm calls from a lower resolution microarray and provides for a true measure of genome-wide performance metrics at the resolution offered by microarray testing. CNV-ROC also provides for a very precise comparison of CNV calls between two microarray platforms without the need to establish an arbitrary degree of overlap. Comparison of CNVs across microarrays is done on a per-probe basis and receiver operator characteristic (ROC) analysis is used to calibrate algorithmic metrics, such as log2 ratio threshold, to enhance CNV calling performance. CNV-ROC addresses a critical and consistently overlooked aspect of analytical assessments of genome-wide techniques like CMAs which is the measurement and use of genome-wide true and false negative data for the calculation of performance metrics and comparison of CNV profiles between different microarray experiments.

Promoting improved utilization of laboratory testing through changes in an electronic medical record: experience at an academic medical center.

This case study over time describes five years of experience with interventions to improve laboratory test utilization at an academic medical center. The high-frequency laboratory tests showing the biggest declines in order volume post intervention were serum albumin (36%) and erythrocyte sedimentation rate (17%). Introduction of restrictions for 170 high-cost send-out tests resulted in a 23% decline in order volume. Targeted interventions reduced mis-orders involving several "look-alike" tests: 1,25-dihydroxyvitamin D, 25-hydroxyvitamin D; manganese, magnesium; beta-2-glycoprotein, beta-2-microglobulin. Lastly, targeted alerts reduced duplicate orders of germline genetic testing and orders of hepatitis B surface antigen within 2 weeks of hepatitis B vaccination.

The heritability of metabolite concentrations in stored human red blood cells.

BACKGROUND: The degeneration of red blood cells (RBCs) during storage is a major issue in transfusion medicine. Family studies in the 1960s established the heritability of the RBC storage lesion based on poststorage adenosine triphosphate (ATP) concentrations. However, this critical discovery has not been further explored. In a classic twin study we confirmed the heritability of poststorage ATP concentrations and established the heritability of many other RBC metabolites. STUDY DESIGN AND METHODS: ATP concentrations and metabolomic profiles were analyzed in RBC samples from 18 twin pairs. On samples stored for 28 days, the heritability of poststorage ATP concentrations were 64 and 53% in CP2D- and AS-3-stored RBCs, respectively. RESULTS: Metabolomic analyses identified 87 metabolites with an estimated heritability of 20% or greater. Thirty-six metabolites were significantly correlated with ATP concentrations (p ≤ 0.05) and 16 correlated with borderline significance (0.05 ≤ p ≤ 0.10). Of the 52 metabolites that correlated significantly with ATP, 24 demonstrated 20% or more heritability. Pathways represented by heritable metabolites included glycolysis, membrane remodeling, redox homeostasis, and synthetic and degradation pathways. CONCLUSION: We conclude that many RBC metabolite concentrations are genetically influenced during storage. Future studies of key metabolic pathways and genetic modifiers of RBC storage could lead to major advances in RBC storage and transfusion therapy.

Mutations in extracellular matrix genes NID1 and LAMC1 cause autosomal dominant Dandy-Walker malformation and occipital cephaloceles.

We performed whole-exome sequencing of a family with autosomal dominant Dandy-Walker malformation and occipital cephaloceles and detected a mutation in the extracellular matrix (ECM) protein-encoding gene NID1. In a second family, protein interaction network analysis identified a mutation in LAMC1, which encodes a NID1-binding partner. Structural modeling of the NID1-LAMC1 complex demonstrated that each mutation disrupts the interaction. These findings implicate the ECM in the pathogenesis of Dandy-Walker spectrum disorders.