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1.  MYBPC1 mutations impair skeletal muscle function in zebrafish models of arthrogryposis 
Human Molecular Genetics  2013;22(24):4967-4977.
Myosin-binding protein C1 (MYBPC1) is an abundant skeletal muscle protein that is expressed predominantly in slow-twitch muscle fibers. Human MYBPC1 mutations are associated with distal arthrogryposis type 1 and lethal congenital contracture syndrome type 4. As MYBPC1 function is incompletely understood, the mechanism by which human mutations result in contractures is unknown. Here, we demonstrate using antisense morpholino knockdown, that mybpc1 is required for embryonic motor activity and survival in a zebrafish model of arthrogryposis. Mybpc1 morphant embryos have severe body curvature, cardiac edema, impaired motor excitation and are delayed in hatching. Myofibril organization is selectively impaired in slow skeletal muscle and sarcomere numbers are greatly reduced in mybpc1 knockdown embryos, although electron microscopy reveals normal sarcomere structure. To evaluate the effects of human distal arthrogryposis mutations, mybpc1 mRNAs containing the corresponding human W236R and Y856H MYBPC1 mutations were injected into embryos. Dominant-negative effects of these mutations were suggested by the resultant mild bent body curvature, decreased motor activity, as well as impaired overall survival compared with overexpression of wild-type RNA. These results demonstrate a critical role for mybpc1 in slow skeletal muscle development and establish zebrafish as a tractable model of human distal arthrogryposis.
PMCID: PMC3836476  PMID: 23873045
2.  Exome Sequencing Identifies a Rare HSPG2 Variant Associated with Familial Idiopathic Scoliosis 
G3: Genes|Genomes|Genetics  2014;5(2):167-174.
Idiopathic scoliosis occurs in 3% of individuals and has an unknown etiology. The objective of this study was to identify rare variants that contribute to the etiology of idiopathic scoliosis by using exome sequencing in a multigenerational family with idiopathic scoliosis. Exome sequencing was completed for three members of this multigenerational family with idiopathic scoliosis, resulting in the identification of a variant in the HSPG2 gene as a potential contributor to the phenotype. The HSPG2 gene was sequenced in a separate cohort of 100 unrelated individuals affected with idiopathic scoliosis and also was examined in an independent idiopathic scoliosis population. The exome sequencing and subsequent bioinformatics filtering resulted in 16 potentially damaging and rare coding variants. One of these variants, p.Asn786Ser, is located in the HSPG2 gene. The variant p.Asn786Ser also is overrepresented in a larger cohort of idiopathic scoliosis cases compared with a control population (P = 0.024). Furthermore, we identified additional rare HSPG2 variants that are predicted to be damaging in two independent cohorts of individuals with idiopathic scoliosis. The HSPG2 gene encodes for a ubiquitous multifunctional protein within the extracellular matrix in which loss of function mutation are known to result in a musculoskeletal phenotype in both mouse and humans. Based on these results, we conclude that rare variants in the HSPG2 gene potentially contribute to the idiopathic scoliosis phenotype in a subset of patients with idiopathic scoliosis. Further studies must be completed to confirm the effect of the HSPG2 gene on the idiopathic scoliosis phenotype.
PMCID: PMC4321025  PMID: 25504735
HSPG2; perlecan; idiopathic scoliosis; exome sequencing
3.  Copy number analysis of 413 isolated talipes equinovarus patients suggests role for transcriptional regulators of early limb development 
Talipes equinovarus is one of the most common congenital musculoskeletal anomalies and has a worldwide incidence of 1 in 1000 births. A genetic predisposition to talipes equinovarus is evidenced by the high concordance rate in twin studies and the increased risk to first-degree relatives. Despite the frequency of isolated talipes equinovarus and the strong evidence of a genetic basis for the disorder, few causative genes have been identified. To identify rare and/or recurrent copy number variants, we performed a genome-wide screen for deletions and duplications in 413 isolated talipes equinovarus patients using the Affymetrix 6.0 array. Segregation analysis within families and gene expression in mouse E12.5 limb buds were used to determine the significance of copy number variants. We identified 74 rare, gene-containing copy number variants that were present in talipes equinovarus probands and not present in 759 controls or in the Database of Genomic Variants. The overall frequency of copy number variants was similar between talipes equinovarus patients compared with controls. Twelve rare copy number variants segregate with talipes equinovarus in multiplex pedigrees, and contain the developmentally expressed transcription factors and transcriptional regulators PITX1, TBX4, HOXC13, UTX, CHD (chromodomain protein)1, and RIPPLY2. Although our results do not support a major role for recurrent copy number variations in the etiology of isolated talipes equinovarus, they do suggest a role for genes involved in early embryonic patterning in some families that can now be tested with large-scale sequencing methods.
PMCID: PMC3598331  PMID: 22892537
talipes equinovarus; microduplication; microdeletion; transcription
4.  Multiplexed direct genomic selection (MDiGS): a pooled BAC capture approach for highly accurate CNV and SNP/INDEL detection 
Nucleic Acids Research  2014;42(10):e82.
Despite declining sequencing costs, few methods are available for cost-effective single-nucleotide polymorphism (SNP), insertion/deletion (INDEL) and copy number variation (CNV) discovery in a single assay. Commercially available methods require a high investment to a specific region and are only cost-effective for large samples. Here, we introduce a novel, flexible approach for multiplexed targeted sequencing and CNV analysis of large genomic regions called multiplexed direct genomic selection (MDiGS). MDiGS combines biotinylated bacterial artificial chromosome (BAC) capture and multiplexed pooled capture for SNP/INDEL and CNV detection of 96 multiplexed samples on a single MiSeq run. MDiGS is advantageous over other methods for CNV detection because pooled sample capture and hybridization to large contiguous BAC baits reduces sample and probe hybridization variability inherent in other methods. We performed MDiGS capture for three chromosomal regions consisting of ∼550 kb of coding and non-coding sequence with DNA from 253 patients with congenital lower limb disorders. PITX1 nonsense and HOXC11 S191F missense mutations were identified that segregate in clubfoot families. Using a novel pooled-capture reference strategy, we identified recurrent chromosome chr17q23.1q23.2 duplications and small HOXC 5′ cluster deletions (51 kb and 12 kb). Given the current interest in coding and non-coding variants in human disease, MDiGS fulfills a niche for comprehensive and low-cost evaluation of CNVs, coding, and non-coding variants across candidate regions of interest.
PMCID: PMC4041413  PMID: 24682816
5.  Pitx1 haploinsufficiency causes clubfoot in humans and a clubfoot-like phenotype in mice 
Human Molecular Genetics  2011;20(20):3943-3952.
Clubfoot affects 1 in 1000 live births, although little is known about its genetic or developmental basis. We recently identified a missense mutation in the PITX1 bicoid homeodomain transcription factor in a family with a spectrum of lower extremity abnormalities, including clubfoot. Because the E130K mutation reduced PITX1 activity, we hypothesized that PITX1 haploinsufficiency could also cause clubfoot. Using copy number analysis, we identified a 241 kb chromosome 5q31 microdeletion involving PITX1 in a patient with isolated familial clubfoot. The PITX1 deletion segregated with autosomal dominant clubfoot over three generations. To study the role of PITX1 haploinsufficiency in clubfoot pathogenesis, we began to breed Pitx1 knockout mice. Although Pitx1+/− mice were previously reported to be normal, clubfoot was observed in 20 of 225 Pitx1+/− mice, resulting in an 8.9% penetrance. Clubfoot was unilateral in 16 of the 20 affected Pitx1+/− mice, with the right and left limbs equally affected, in contrast to right-sided predominant hindlimb abnormalities previously noted with complete loss of Pitx1. Peroneal artery hypoplasia occurred in the clubfoot limb and corresponded spatially with small lateral muscle compartments. Tibial and fibular bone volumes were also reduced. Skeletal muscle gene expression was significantly reduced in Pitx1−/− E12.5 hindlimb buds compared with the wild-type, suggesting that muscle hypoplasia was due to abnormal early muscle development and not disuse atrophy. Our morphological data suggest that PITX1 haploinsufficiency may cause a developmental field defect preferentially affecting the lateral lower leg, a theory that accounts for similar findings in human clubfoot.
PMCID: PMC3177645  PMID: 21775501
6.  Exome-Sequencing Confirms DNAJC5 Mutations as Cause of Adult Neuronal Ceroid-Lipofuscinosis 
PLoS ONE  2011;6(11):e26741.
We performed whole-exome sequencing in two autopsy-confirmed cases and an elderly unaffected control from a multigenerational family with autosomal dominant neuronal ceroid lipofuscinosis (ANCL). A novel single-nucleotide variation (c.344T>G) in the DNAJC5 gene was identified. Mutational screening in an independent family with autosomal dominant ANCL found an in-frame single codon deletion (c.346_348 delCTC) resulting in a deletion of p.Leu116del. These variants fulfill all genetic criteria for disease-causing mutations: they are found in unrelated families with the same disease, exhibit complete segregation between the mutation and the disease, and are absent in healthy controls. In addition, the associated amino acid substitutions are located in evolutionarily highly conserved residues and are predicted to functionally affect the encoded protein (CSPα). The mutations are located in a cysteine-string domain, which is required for membrane targeting/binding, palmitoylation, and oligomerization of CSPα. We performed a comprehensive in silico analysis of the functional and structural impact of both mutations on CSPα. We found that these mutations dramatically decrease the affinity of CSPα for the membrane. We did not identify any significant effect on palmitoylation status of CSPα. However, a reduction of CSPα membrane affinity may change its palmitoylation and affect proper intracellular sorting. We confirm that CSPα has a strong intrinsic aggregation propensity; however, it is not modified by the mutations. A complementary disease-network analysis suggests a potential interaction with other NCLs genes/pathways. This is the first replication study of the identification of DNAJC5 as the disease-causing gene for autosomal dominant ANCL. The identification of the novel gene in ANCL will allow us to gain a better understanding of the pathological mechanism of ANCLs and constitutes a great advance toward the development of new molecular diagnostic tests and may lead to the development of potential therapies.
PMCID: PMC3208569  PMID: 22073189
7.  An RNAi-Based Screen of Transcription Factor Genes Identifies Pathways Necessary for Sensory Regeneration in the Avian Inner Ear 
Sensory hair cells of the inner ear are the mechano-electric transducers of sound and head motion. In mammals, damage to sensory hair cells leads to hearing or balance deficits. Non-mammalian vertebrates such as birds can regenerate hair cells after injury. In a previous study, we characterized transcription factor gene expression during chicken hair cell regeneration. In those studies, a laser micro-beam or ototoxic antibiotics were used to damage the sensory epithelia (SE). The current study focused on 27 genes that were up-regulated in regenerating SE compared to untreated SE in the previous study. Those genes were knocked down by siRNA, to determine their requirement for supporting cell proliferation and to measure resulting changes in the larger network of gene expression. We identified 11 genes necessary for proliferation and also identified novel interactive relationships between many of them. Defined components of the WNT, PAX and AP1 pathways were shown to be required for supporting cell proliferation. These pathways intersect on WNT4, which is also necessary for proliferation. Among the required genes, the CCAAT enhancer binding protein, CEBPG, acts downstream of Jun Kinase and JUND in the AP1 pathway. The WNT co-receptor LRP5 acts downstream of CEBPG as does the transcription factor BTAF1. Both of these genes are also necessary for supporting cell proliferation. This is the first large scale screen of its type and suggests an important intersection between the AP1 pathway, the PAX pathway and WNT signaling in the regulation of supporting cell proliferation during inner ear hair cell regeneration.
PMCID: PMC3086586  PMID: 21430154
8.  Chikungunya Virus Induces IPS-1-Dependent Innate Immune Activation and Protein Kinase R-Independent Translational Shutoff▿  
Journal of Virology  2010;85(1):606-620.
Chikungunya virus (CHIKV) is an arthritogenic mosquito-transmitted alphavirus that is undergoing reemergence in areas around the Indian Ocean. Despite the current and potential danger posed by this virus, we know surprisingly little about the induction and evasion of CHIKV-associated antiviral immune responses. With this in mind we investigated innate immune reactions to CHIKV in human fibroblasts, a demonstrable in vivo target of virus replication and spread. We show that CHIKV infection leads to activation of the transcription factor interferon regulatory factor 3 (IRF3) and subsequent transcription of IRF3-dependent antiviral genes, including beta interferon (IFN-β). IRF3 activation occurs by way of a virus-induced innate immune signaling pathway that includes the adaptor molecule interferon promoter stimulator 1 (IPS-1). Despite strong transcriptional upregulation of these genes, however, translation of the corresponding proteins is not observed. We further demonstrate that translation of cellular (but not viral) genes is blocked during infection and that although CHIKV is found to trigger inactivation of the translational molecule eukaryotic initiation factor subunit 2α by way of the double-stranded RNA sensor protein kinase R, this response is not required for the block to protein synthesis. Furthermore, overall diminution of cellular RNA synthesis is also observed in the presence of CHIKV and transcription of IRF3-dependent antiviral genes appears specifically blocked late in infection. We hypothesize that the observed absence of IFN-β and antiviral proteins during infection results from an evasion mechanism exhibited by CHIKV that is dependent on widespread shutoff of cellular protein synthesis and a targeted block to late synthesis of antiviral mRNA transcripts.
PMCID: PMC3014158  PMID: 20962078
9.  Downstream Targets of GATA3 in the Vestibular Sensory Organs of the Inner Ear 
Haploinsufficiency for the transcription factor GATA3 leads to hearing loss in humans. It is expressed throughout the auditory sensory epithelium (SE). In the vestibular organs, GATA3 is limited to the striola reversal zone of the utricle. Stereocilia orientation shifts 180° at this region which contains morphologically-distinct type I hair cells. The striola is conserved in all amniotes, its function is unknown and GATA3 is the only known marker of the reversal zone. To identify downstream targets of GATA3 that might point to striolar function we measured gene expression differences between striolar and extra-striolar SE. These were compared with profiles after GATA3 RNAi and GATA3 over-expression. We identified four genes (BMP2, FKHL18, LMO4 and MBNL2) that consistently varied with GATA3. Two of these (LMO4 and MBNL2) were shown to be direct targets of GATA3 by ChIP. Our results suggest that GATA3 impacts WNT signaling in this region of the sensory macula.
PMCID: PMC3086404  PMID: 19924793
Transcription Factors; Inner Ear; Utricle
10.  Activation of the Interferon Response by Human Cytomegalovirus Occurs via Cytoplasmic Double-Stranded DNA but Not Glycoprotein B ▿  
Journal of Virology  2010;84(17):8913-8925.
In vitro infection of cells with the betaherpesvirus human cytomegalovirus (HCMV) stimulates an innate immune response characterized by phosphorylation of the transcription factor interferon regulatory factor 3 (IRF3) and subsequent expression of IRF3-dependent genes. While previous work suggests that HCMV envelope glycoprotein B is responsible for initiating this reaction, the signaling pathways stimulated by virus infection that lead to IRF3 phosphorylation have largely been uncharacterized. Recently, we identified Z DNA binding protein 1 (ZBP1), a sensor of cytoplasmic DNA, as an essential protein for this response. We now describe a human fibroblast cell line exhibiting a recessive defect that results in the absence of activation of IRF3 following treatment with HCMV but not Sendai virus or double-stranded RNA. In addition, we show that while exposure of these cells to soluble HCMV glycoprotein B is capable of triggering IRF3-dependent gene transcription, transfection of the cells with double-stranded DNA is not. Furthermore, we show that overexpression of ZBP1 in these cells reestablishes their ability to secrete interferon in response to HCMV and that multiple ZBP1 transcriptional variants exist in both wild-type and mutant cells. These results have two major implications for the understanding of innate immune stimulation by HCMV. First, they demonstrate that HCMV glycoprotein B is not the essential molecular pattern that induces an IRF3-dependent innate immune response. Second, IRF3-terminal signaling triggered by HCMV particles closely resembles that which is activated by cytoplasmic double-stranded DNA.
PMCID: PMC2919031  PMID: 20573816
11.  Human Cytomegalovirus Induces the Interferon Response via the DNA Sensor ZBP1▿  
Journal of Virology  2009;84(1):585-598.
Human cytomegalovirus (HCMV) is a member of the betaherpesvirus family that, unlike other herpesviruses, triggers a strong innate immune response in infected cells that includes transcription of the beta interferon gene via activation of interferon regulatory factor 3 (IRF3). IRF3 activation requires signaling from pattern recognition receptors that is initiated by their interaction with specific pathogen-associated molecules. However, while IRF3-activating pathways are increasingly well characterized, the cellular molecules involved in HCMV-mediated IRF3-dependent beta interferon transcription are virtually unknown. We undertook a systematic examination of new and established IRF3-terminal pathway components to identify those that are essential to HCMV-triggered IRF3 activation. We show here that IRF3 activation induced by HCMV infection involves the newly identified protein STING but, in contrast to infections with other herpesviruses, occurs independently of the adaptor molecule IPS-1. We also show that the protein DDX3 contributes to HCMV-triggered expression of beta interferon. Moreover, we identify Z-DNA binding protein 1 (ZBP1) as being essential for IRF3 activation and interferon beta expression triggered by HCMV, as well as being sufficient to enhance HCMV-stimulated beta interferon transcription and secretion. ZBP1 transcription was also found to be induced following exposure to HCMV in a JAK/STAT-dependent manner, thus perhaps also contributing to a positive feedback signal. Finally, we show that constitutive overexpression of ZBP1 inhibits HCMV replication. ZBP1 was recently identified as a cytosolic pattern recognition receptor of double-stranded DNA, and thus, we propose a model for HCMV-mediated IRF3 activation that involves HCMV-associated DNA as the principal innate immune-activating pathogen-associated molecular pattern.
PMCID: PMC2798427  PMID: 19846511
12.  Large Scale Gene Expression Profiles of Regenerating Inner Ear Sensory Epithelia 
PLoS ONE  2007;2(6):e525.
Loss of inner ear sensory hair cells (HC) is a leading cause of human hearing loss and balance disorders. Unlike mammals, many lower vertebrates can regenerate these cells. We used cross-species microarrays to examine this process in the avian inner ear. Specifically, changes in expression of over 1700 transcription factor (TF) genes were investigated in hair cells of auditory and vestibular organs following treatment with two different damaging agents and regeneration in vitro. Multiple components of seven distinct known signaling pathways were clearly identifiable: TGFβ, PAX, NOTCH, WNT, NFKappaB, INSULIN/IGF1 and AP1. Numerous components of apoptotic and cell cycle control pathways were differentially expressed, including p27KIP and TFs that regulate its expression. A comparison of expression trends across tissues and treatments revealed identical patterns of expression that occurred at identical times during regenerative proliferation. Network analysis of the patterns of gene expression in this large dataset also revealed the additional presence of many components (and possible network interactions) of estrogen receptor signaling, circadian rhythm genes and parts of the polycomb complex (among others). Equal numbers of differentially expressed genes were identified that have not yet been placed into any known pathway. Specific time points and tissues also exhibited interesting differences: For example, 45 zinc finger genes were specifically up-regulated at later stages of cochlear regeneration. These results are the first of their kind and should provide the starting point for more detailed investigations of the role of these many pathways in HC recovery, and for a description of their possible interactions.
PMCID: PMC1888727  PMID: 17565378

Results 1-12 (12)