Bio

Professional Education


  • Bachelor of Science, McMaster University (2004)
  • Master of Science, University of Western Ontario (2006)
  • Doctor of Philosophy, University of Western Ontario (2011)

Stanford Advisors


Publications

Journal Articles


  • Panx1 Regulates Cellular Properties of Keratinocytes and Dermal Fibroblasts in Skin Development and Wound Healing. The Journal of investigative dermatology Penuela, S., Kelly, J. J., Churko, J. M., Barr, K., Berger, A. C., Laird, D. W. 2014

    Abstract

    Pannexin1 (Panx1), a channel-forming glycoprotein is expressed in neonatal but not aged mouse skin. Histological staining of Panx1 knockout (KO) mouse skin revealed a reduction in epidermal and dermal thickness but an increase in hypodermal adipose tissue. Following dorsal skin punch biopsies, mutant mice exhibited a significant delay in wound healing. Scratch wound and proliferation assays revealed that cultured keratinocytes from KO mice were more migratory while dermal fibroblasts were more proliferative than controls. Additionally, collagen gels populated with fibroblasts from KO mice exhibited significantly reduced contraction, comparable to WT fibroblasts treated with the Panx1 blocker, probenecid. KO fibroblasts did not increase α-smooth muscle actin expression in response to TGF-β, as is the case for differentiating WT myofibroblasts during wound contraction. We conclude that Panx1 controls cellular properties of keratinocytes and dermal fibroblasts during early stages of skin development and modulates wound repair upon injury.Journal of Investigative Dermatology accepted article preview online, 12 February 2014; doi:10.1038/jid.2014.86.

    View details for DOI 10.1038/jid.2014.86

    View details for PubMedID 24522432

  • Overview of high throughput sequencing technologies to elucidate molecular pathways in cardiovascular diseases. Circulation research Churko, J. M., Mantalas, G. L., Snyder, M. P., Wu, J. C. 2013; 112 (12): 1613-1623

    Abstract

    High throughput sequencing technologies have become essential in studies on genomics, epigenomics, and transcriptomics. Although sequencing information has traditionally been elucidated using a low throughput technique called Sanger sequencing, high throughput sequencing technologies are capable of sequencing multiple DNA molecules in parallel, enabling hundreds of millions of DNA molecules to be sequenced at a time. This advantage allows high throughput sequencing to be used to create large data sets, generating more comprehensive insights into the cellular genomic and transcriptomic signatures of various diseases and developmental stages. Within high throughput sequencing technologies, whole exome sequencing can be used to identify novel variants and other mutations that may underlie many genetic cardiac disorders, whereas RNA sequencing can be used to analyze how the transcriptome changes. Chromatin immunoprecipitation sequencing and methylation sequencing can be used to identify epigenetic changes, whereas ribosome sequencing can be used to determine which mRNA transcripts are actively being translated. In this review, we will outline the differences in various sequencing modalities and examine the main sequencing platforms on the market in terms of their relative read depths, speeds, and costs. Finally, we will discuss the development of future sequencing platforms and how these new technologies may improve on current sequencing platforms. Ultimately, these sequencing technologies will be instrumental in further delineating how the cardiovascular system develops and how perturbations in DNA and RNA can lead to cardiovascular disease.

    View details for DOI 10.1161/CIRCRESAHA.113.300939

    View details for PubMedID 23743227

  • Gap junction remodeling in skin repair following wounding and disease. Physiology Churko, J. M., Laird, D. W. 2013; 28 (3): 190-198

    Abstract

    In the present review, we provide an overview of connexin expression during skin development and remodeling in wound healing, and reflect on how loss- or gain-of-function connexin mutations may change cellular phenotypes and lead to diseases of the skin. We also consider the therapeutic value of targeting connexins in wound healing.

    View details for DOI 10.1152/physiol.00058.2012

    View details for PubMedID 23636264

  • Generation of Human iPSCs from Human Peripheral Blood Mononuclear Cells Using Non-integrative Sendai Virus in Chemically Defined Conditions. Methods in molecular biology (Clifton, N.J.) Churko, J. M., Burridge, P. W., Wu, J. C. 2013; 1036: 81-88

    Abstract

    Human-induced pluripotent stem cells (hiPSCs) have received enormous attention because of their ability to differentiate into multiple cell types that demonstrate the patient's original phenotype. The use of hiPSCs is particularly valuable to the study of cardiac biology, as human cardiomyocytes are difficult to isolate and culture and have a limited proliferative potential. By deriving iPSCs from patients with heart disease and subsequently differentiating these hiPSCs to cardiomyocytes, it is feasible to study cardiac biology in vitro and model cardiac diseases. While there are many different methods for deriving hiPSCs, clinical use of these hiPSCs will require derivation by methods that do not involve modification of the original genome (non-integrative) or incorporate xeno-derived products (such as bovine serum albumin) which may contain xeno-agents. Ideally, this derivation would be carried out under chemically defined conditions to prevent lot-to-lot variability and enhance reproducibility. Additionally, derivation from cell types such as fibroblasts requires extended culture (4-6 weeks), greatly increasing the time required to progress from biopsy to hiPSC. Herein, we outline a method of culturing peripheral blood mononuclear cells (PBMCs) and reprogramming PBMCs into hiPSCs using a non-integrative Sendai virus.

    View details for DOI 10.1007/978-1-62703-511-8_7

    View details for PubMedID 23807788

  • Loss of Pannexin 1 Attenuates Melanoma Progression by Reversion to a Melanocytic Phenotype JOURNAL OF BIOLOGICAL CHEMISTRY Penuela, S., Gyenis, L., Ablack, A., Churko, J. M., Berger, A. C., Litchfield, D. W., Lewis, J. D., Laird, D. W. 2012; 287 (34): 29184-29193

    Abstract

    Pannexin 1 (Panx1) is a channel-forming glycoprotein expressed in different cell types of mammalian skin. We examined the role of Panx1 in melanoma tumorigenesis and metastasis since qPCR and Western blots revealed that mouse melanocytes exhibited low levels of Panx1 while increased Panx1 expression was correlated with tumor cell aggressiveness in the isogenic melanoma cell lines (B16-F0, -F10, and -BL6). Panx1 shRNA knockdown (Panx1-KD) generated stable BL6 cell lines, with reduced dye uptake, that showed a marked increase in melanocyte-like cell characteristics including higher melanin production, decreased cell migration and enhanced formation of cellular projections. Western blotting and proteomic analyses using 2D-gel/mass spectroscopy identified vimentin and ?-catenin as two of the markers of malignant melanoma that were down-regulated in Panx1-KD cells. Xenograft Panx1-KD cells grown within the chorioallantoic membrane of avian embryos developed tumors that were significantly smaller than controls. Mouse-Alu qPCR of the excised avian embryonic organs revealed that tumor metastasis to the liver was significantly reduced upon Panx1 knockdown. These data suggest that while Panx1 is present in skin melanocytes it is up-regulated during melanoma tumor progression, and tumorigenesis can be inhibited by the knockdown of Panx1 raising the possibility that Panx1 may be a viable target for the treatment of melanoma.

    View details for DOI 10.1074/jbc.M112.377176

    View details for Web of Science ID 000308074600084

    View details for PubMedID 22753409

  • The G60S Cx43 mutant enhances keratinocyte proliferation and differentiation EXPERIMENTAL DERMATOLOGY Churko, J. M., Kelly, J. J., Macdonald, A., Lee, J., Sampson, J., Bai, D., Laird, D. W. 2012; 21 (8): 612-618

    Abstract

    Transient knock-down of the gap junction protein Cx43 by antisense and siRNA, or gap junction block with mimetic peptides, have been shown to enhance epidermal wound healing. However, patients with oculodentodigital dysplasia (ODDD) express mutant Cx43 that leads to a chronic reduction in gap junctional intercellular communication. To determine whether mutant Cx43 in keratinocytes would impact upon the wound healing process, we localized Cx43 in human and mouse skin tissue expressing mutant Cx43 and assessed the ability of primary keratinocytes derived from a mouse model of ODDD to proliferate, migrate and differentiate. In the epidermis from an ODDD patient and in the epidermis of mice expressing the G60S mutant or in keratinocytes obtained from mutant mice, Cx43 was frequently found within intracellular compartments and rarely localized to punctate sites of cell-cell apposition. Primary keratinocytes derived from G60S mutant mice proliferated faster but migrated similarly to keratinocytes derived from wild-type control mice. Keratinocytes derived from mutant mice expressed abundant Cx43 and higher levels of involucrin and loricrin under low calcium conditions. However, after calcium-induced differentiation, similar levels of Cx43, involucrin and loricrin were observed. Thus, we conclude that during wound healing, mutant Cx43 may enhance keratinocyte proliferation and promote early differentiation of keratinocytes.

    View details for DOI 10.1111/j.1600-0625.2012.01532.x

    View details for Web of Science ID 000306222700009

    View details for PubMedID 22775996

  • The G60S Connexin43 Mutant Regulates Hair Growth and Hair Fiber Morphology in a Mouse Model of Human Oculodentodigital Dysplasia JOURNAL OF INVESTIGATIVE DERMATOLOGY Churko, J. M., Chan, J., Shao, Q., Laird, D. W. 2011; 131 (11): 2197-2204

    Abstract

    Patients expressing mutations in the gene encoding the gap junction protein Cx43 suffer from a disease called oculodentodigital dysplasia (ODDD). Patients with ODDD are often reported to develop hair that is dry, dull, sparse, and slow growing. To evaluate the linkage between Cx43 and hair growth, structure, and follicle density we employed a mouse model of ODDD that harbors a Cx43 G60S point mutant. Regionally sparse and overall dull hair were observed in mutant mice compared with their wild-type (WT) littermates. However, histological analysis of overall hair follicle density in mutant and WT mice did not reveal any significant differences. After epilation, mutant mouse hair grew back slower, and hair growth was asynchronous. In addition, ultrastructural scanning electron microscopic imaging of hair fibers taken from mutant mice and two patients harboring the G143S mutation revealed severe cuticle weathering. Nodule formation was also observed in the proximal region of hair fibers taken from mutant mice. These results suggest that the G60S mutant mouse model mimics the hair phenotype found in at least some ODDD patients and suggests an important role for Cx43 in hair regeneration, growth, and cuticle formation.

    View details for DOI 10.1038/jid.2011.183

    View details for Web of Science ID 000296240100013

    View details for PubMedID 21716323

  • Human Dermal Fibroblasts Derived from Oculodentodigital Dysplasia Patients Suggest That Patients May Have Wound-Healing Defects HUMAN MUTATION Churko, J. M., Shao, Q., Gong, X., Swoboda, K. J., Bai, D., Sampson, J., Laird, D. W. 2011; 32 (4): 456-466

    Abstract

    Oculodentodigital dysplasia (ODDD) is primarily an autosomal dominant human disease caused by any one of over 60 mutations in the GJA1 gene encoding the gap junction protein Cx43. In the present study, wound healing was investigated in a G60S ODDD mutant mouse model and by using dermal fibroblasts isolated from two ODDD patients harboring the p.D3N and p.V216L mutants along with dermal fibroblasts isolated from their respective unaffected relatives. Punch biopsies revealed a delay in wound closure in the G60S mutant mice in comparison to wild-type littermates, and this delay appeared to be due to defects in the dermal fibroblasts. Although both the p.D3N and p.V216L mutants reduced gap junctional intercellular communication in human dermal fibroblasts, immunolocalization studies revealed that Cx43 gap junctions were prevalent at the cell surface of p.D3N expressing fibroblasts but greatly reduced in p.V216L expressing fibroblasts. Mutant expressing fibroblasts were further found to have reduced proliferation and migration capabilities. Finally, in response to TGF?1, mutant expressing fibroblasts expressed significantly less alpha smooth muscle actin suggesting they were inefficient in their ability to differentiate into myofibroblasts. Collectively, our results suggest that ODDD patients may have subclinical defects in wound healing due to impaired function of dermal fibroblasts.

    View details for DOI 10.1002/humu.21472

    View details for Web of Science ID 000288464100018

    View details for PubMedID 21305658

  • The potency of the fs260 connexin43 mutant to impair keratinocyte differentiation is distinct from other disease-linked connexin43 mutants BIOCHEMICAL JOURNAL Churko, J. M., Langlois, S., Pan, X., Shao, Q., Laird, D. W. 2010; 429: 473-483

    Abstract

    Although there are currently 62 mutants of Cx43 (connexin43) that can cause ODDD (oculodentodigital dysplasia), only two mutants have also been reported to cause palmar plantar hyperkeratosis. To determine how mutants of Cx43 can lead to this skin disease, REKs (rat epidermal keratinocytes) were engineered to express an ODDD-associated Cx43 mutant always linked to skin disease (fs260), an ODDD-linked Cx43 mutant which has been reported to sometimes cause skin disease (fs230), Cx43 mutants which cause ODDD only (G21R, G138R), a mouse Cx43 mutant linked to ODDD (G60S), a non-disease-linked truncated Cx43 mutant that is trapped in the endoplasmic reticulum (Delta244*) or full-length Cx43. When grown in organotypic cultures, of all the mutants investigated, only the fs260-expressing REKs consistently developed a thinner stratum corneum and expressed lower levels of Cx43, Cx26 and loricrin in comparison with REKs overexpressing wild-type Cx43. REKs expressing the fs260 mutant also developed a larger organotypic vital layer after acetone-induced injury and exhibited characteristics of parakeratosis. Collectively, our results suggest that the increased skin disease burden exhibited in ODDD patients harbouring the fs260 mutant is probably due to multiple additive effects cause by the mutant during epidermal differentiation.

    View details for DOI 10.1042/BJ20100155

    View details for Web of Science ID 000280625400006

    View details for PubMedID 20515445

  • Implications of pannexin 1 and pannexin 3 for keratinocyte differentiation JOURNAL OF CELL SCIENCE Celetti, S. J., Cowan, K. N., Penuela, S., Shao, Q., Churko, J., Laird, D. W. 2010; 123 (8): 1363-1372

    Abstract

    Pannexin (Panx) 1 and Panx3 are integral membrane proteins that share some sequence homology with the innexin family of invertebrate gap junctions. They are expressed in mammalian skin. Pannexins have been reported to form functional mechanosensitive single-membrane channels, but their importance in regulating cellular function is poorly understood. In this study, Panx1 and Panx3 were detected in the epidermis of 13.5 day embryonic mice. Compared with newborn mice, there was less Panx1 expression in both thin and thick murine skin, whereas Panx3 expression was unchanged. To investigate the role of pannexins in keratinocyte differentiation, we employed rat epidermal keratinocytes (REKs) that have the capacity to differentiate into organotypic epidermis, and engineered them to overexpress Panx1, Panx1-GFP or Panx3. The expression of Panx1 or Panx3 resulted in the increased ability of REKs to take up dye, suggesting that cell-surface channels were formed. Compared with monolayer REKs, endogenous Panx1 levels remained unchanged, whereas the 70 kDa immunoreactive species of Panx3 was greatly increased in the organotypic epidermis. In monolayer cultures, ectopic Panx1 and Panx1-GFP localized to the plasma membrane, whereas Panx3 displayed both intracellular and plasma-membrane profiles. Although both pannexins reduced cell proliferation, only Panx1 disrupted the architecture of the organotypic epidermis and markedly dysregulated cytokeratin 14 expression and localization. Furthermore, ectopic expression of only Panx1 reduced the vital layer thickness of the organotypic epidermis. In summary, Panx1 and Panx3 are coexpressed in the mammalian epidermis, and the regulation of Panx1 plays a key role in keratinocyte differentiation.

    View details for DOI 10.1242/jcs.056093

    View details for Web of Science ID 000276568200019

    View details for PubMedID 20332104

  • Pannexin1 and Pannexin3 Delivery, Cell Surface Dynamics, and Cytoskeletal Interactions JOURNAL OF BIOLOGICAL CHEMISTRY Bhalla-Gehi, R., Penuela, S., Churko, J. M., Shao, Q., Laird, D. W. 2010; 285 (12): 9147-9160

    Abstract

    Pannexins (Panx) are a class of integral membrane proteins that have been proposed to exhibit characteristics similar to those of connexin family members. In this study, we utilized Cx43-positive BICR-M1R(k) cells to stably express Panx1, Panx3, or Panx1-green fluorescent protein (GFP) to assess their trafficking, cell surface dynamics, and interplay with the cytoskeletal network. Expression of a Sar1 dominant negative mutant revealed that endoplasmic reticulum to Golgi transport of Panx1 and Panx3 was mediated via COPII-dependent vesicles. Distinct from Cx43-GFP, fluorescence recovery after photobleaching studies revealed that both Panx1-GFP and Panx3-GFP remained highly mobile at the cell surface. Unlike Cx43, Panx1-GFP exhibited no detectable interrelationship with microtubules. Conversely, cytochalasin B-induced disruption of microfilaments caused a severe loss of cell surface Panx1-GFP, a reduction in the recoverable fraction of Panx1-GFP that remained at the cell surface, and a decrease in Panx1-GFP vesicular transport. Furthermore, co-immunoprecipitation and co-sedimentation assays revealed actin as a novel binding partner of Panx1. Collectively, we conclude that although Panx1 and Panx3 share a common endoplasmic reticulum to Golgi secretory pathway to Cx43, their ultimate cell surface residency appears to be independent of cell contacts and the need for intact microtubules. Importantly, Panx1 has an interaction with actin microfilaments that regulates its cell surface localization and mobility.

    View details for DOI 10.1074/jbc.M109.082008

    View details for Web of Science ID 000275553700064

    View details for PubMedID 20086016

  • Optical and biochemical dissection of connexin and disease-linked connexin mutants in 3D organotypic epidermis. Methods in molecular biology (Clifton, N.J.) Langlois, S., Churko, J. M., Laird, D. W. 2010; 585: 313-334

    Abstract

    The epidermis is a complex tissue composed principally of differentiated keratinocytes that form a keratinized stratified squamous epithelium. The gap junction proteins, connexins (Cx), are differentially expressed throughout the stratified layers of the epidermis and their exquisite regulation appears to govern the delicate balance between cell proliferation and differentiation in normal skin homeostasis and in wound healing. In the last 10 years, germ line mutations in the genes encoding five connexin family members have been linked to various types of skin diseases that appear to offset the balance between keratinocyte differentiation and proliferation. Consequently, in order to determine how these connexin gene mutations manifest as skin disease, disease-linked mutants must be expressed in 3D organotypic epidermis reference models that attempt to mimic the human condition. Given the complexity of organotypic epidermis, confocal optical and biochemical dissection of connexin or disease-linked connexin mutants within the regenerated epidermal layer is required. The procedures necessary to assess the architectural characteristics of genetically modified organotypic epidermis and its state of differentiation will be described in this chapter.

    View details for DOI 10.1007/978-1-60761-380-0_22

    View details for PubMedID 19908013

  • Cx43 has distinct mobility within plasma-membrane domains, indicative of progressive formation of gap-junction plaques JOURNAL OF CELL SCIENCE Simek, J., Churko, J., Shao, Q., Laird, D. W. 2009; 122 (4): 554-562

    Abstract

    Connexin 43 (Cx43) is a dynamic molecule, having a short half-life of only a few hours. In this study, we use fluorescent-protein-tagged Cx43 variants to examine Cx43 delivery to the cell surface, its residency status in various cell-surface membrane domains and its mobility characteristics. Rapid time-lapse imaging led to the identification of Cx43 being delivered to cell-surface domains that lacked a contacting cell, and also to its localization within membrane protrusions. Fluorescence recovery after photobleaching (FRAP) was used to investigate the mobility state of cell-surface-localized Cx43. Cx43 mobility within clustered cell-surface profiles of Cx43 could be categorized into those with generally a high degree of lateral mobility and those with generally a low degree of lateral mobility. Cx43 mobility was independent of cluster size, yet the C-terminal domain of Cx43 regulated the proportion of gap-junction-like clusters that acquired a low Cx43 mobility state. Collectively, these studies show that Cx43 establishes residency at all cell-surface membrane domains, and progressively acquires assembly states that probably reflect differences in either channel packing and/or its interactions with Cx43-binding proteins.

    View details for DOI 10.1242/jcs.036970

    View details for Web of Science ID 000263071700014

    View details for PubMedID 19174466

  • Fate of connexin43 in cardiac tissue harbouring a disease-linked connexin43 mutant CARDIOVASCULAR RESEARCH Manias, J. L., Plante, I., Gong, X., Shao, Q., Churko, J., Bai, D., Laird, D. W. 2008; 80 (3): 385-395

    Abstract

    More than 40 mutations in the GJA1 gene encoding connexin43 (Cx43) have been linked to oculodentodigital dysplasia (ODDD), a pleiotropic, autosomal dominant disorder. We hypothesized that even with a significant reduction in the levels of Cx43 in a mutant mouse model of ODDD (Gja1(Jrt/+)) harbouring a G60S mutation (Cx43(G60S)), cardiomyocyte function may only be moderately compromised given that a majority of mutant mice typically survive.Western blotting and quantitative reverse transcriptase-polymerase chain reaction in conjunction with immunofluorescence were used to assess the expression and localization of Cx43 in hearts and cultured cardiomyocytes from wild-type and Gja1(Jrt/+) mice. Dye-coupling and dual whole cell patch-clamp recordings were also used to assess the gap junction channel status in cultured cardiomyocytes from wild-type and mutant mice. Cardiac tissue from adult Gja1(Jrt/+) mice revealed a 60-80% reduction in Cx43 protein with a preferential loss of the highly phosphorylated forms of Cx43. Compensation via the up-regulation of Cx40 or Cx45 was not observed. Immunofluorescent analysis of cultured cardiomyocytes revealed a trafficking defect, with a decrease in Cx43 plaques and a large population of Cx43 being retained in the Golgi apparatus. However, cultured cardiomyocytes from mutant mice remained beating with a 50% decrease in coupling conductance.These results suggest that the Cx43(G60S) mutant impairs normal trafficking and function of co-expressed Cx43 with no dramatic effect on cardiomyocyte function, suggesting that Cx43 is biosynthesized in excess of an essential need.

    View details for DOI 10.1093/cvr/cvn203

    View details for Web of Science ID 000260973500011

    View details for PubMedID 18678643

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