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ABSTRACT: Low back pain is a significant socioeconomic burden and intervertebral disc degeneration has been implicated as a cause. A reliable animal model of disc degeneration is necessary to evaluate therapeutics, and functional metrics are essential to quantify their benefit. To this end, needle puncture injuries were created in the caudal intervertebral discs of mice to induce disc degeneration. Compression, torsion, and creep mechanics were assessed both immediately and after eight weeks to distinguish between the effects of injury and the subsequent reparative or degenerative response. Two needle sizes (29 and 26 gauge) were used to determine injury size-dependence. Compressive stiffness (62%), torsional stiffness (60%), and early damping stiffness (84%) decreased immediately after injury with the large needle (26G). These mechanical properties did not change over time despite structural and compositional changes. At 8 weeks following large needle injury, disc height decreased (37%), nucleus pulposus (NP) glycosaminoglycan content decreased (41%), and NP collagen content increased (45%). The small needle size had no significant effect on mechanics and did not initiate degenerative changes in structure and composition. Thus, the injection of therapeutics into the NP with a minimal needle size may limit damage due to the needle insertion. These findings, along with the wide commercial availability of mouse-specific biological probes, indicate that the mouse caudal disc model can be a powerful tool for investigating disc degeneration and therapy. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res.
Journal of Orthopaedic Research 04/2013; · 2.81 Impact Factor
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ABSTRACT: Muscle progenitor cells migrate from the lateral somites into the developing vertebrate limb, where they undergo patterning and differentiation in response to local signals. Sonic hedgehog (Shh) is a secreted molecule made in the posterior limb bud that affects patterning and development of multiple tissues, including skeletal muscles. However, the cell-autonomous and non-cell-autonomous functions of Shh during limb muscle formation have remained unclear. We found that Shh affects the pattern of limb musculature non-cell-autonomously, acting through adjacent nonmuscle mesenchyme. However, Shh plays a cell-autonomous role in maintaining cell survival in the dermomyotome and initiating early activation of the myogenic program in the ventral limb. At later stages, Shh promotes slow muscle differentiation cell-autonomously. In addition, Shh signaling is required cell-autonomously to regulate directional muscle cell migration in the distal limb. We identify neuroepithelial cell transforming gene 1 (Net1) as a downstream target and effector of Shh signaling in that context.
Genes & development 09/2012; 26(18):2088-102. · 12.08 Impact Factor
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ABSTRACT: The intervertebral discs, located between adjacent vertebrae, are required for stability of the spine and distributing mechanical load throughout the vertebral column. All cell types located in the middle regions of the discs, called nuclei pulposi, are derived from the embryonic notochord. Recently, it was shown that the hedgehog signaling pathway plays an essential role during formation of nuclei pulposi. However, during the time that nuclei pulposi are forming, Shh is expressed in both the notochord and the nearby floor plate. To determine the source of SHH protein sufficient for formation of nuclei pulposi we removed Shh from either the floor plate or the notochord using tamoxifen-inducible Cre alleles. Removal of Shh from the floor plate resulted in phenotypically normal intervertebral discs, indicating that Shh expression in this tissue is not required for disc patterning. In addition, embryos that lacked Shh in the floor plate had normal vertebral columns, demonstrating that Shh expression in the notochord is sufficient for pattering the entire vertebral column. Removal of Shh from the notochord resulted in the absence of Shh in the floor plate, loss of intervertebral discs and vertebral structures. These data indicate that Shh expression in the notochord is sufficient for patterning of the intervertebral discs and the vertebral column.
Mechanisms of development 07/2012; 129(9-12):255-62. · 2.83 Impact Factor
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ABSTRACT: Gene silencing mediated by either microRNAs (miRNAs) or Adenylate/uridylate-rich elements Mediated mRNA Degradation (AMD) is a powerful way to post-transcriptionally modulate gene expression. We and others have reported that the RNA-binding protein KSRP favors the biogenesis of select miRNAs (including let-7 family) and activates AMD promoting the decay of inherently labile mRNAs. Different layers of interplay between miRNA- and AMD-mediated gene silencing have been proposed in cultured cells, but the relationship between the two pathways in living organisms is still elusive. We conditionally deleted Dicer in mouse pituitary from embryonic day (E) 9.5 through Cre-mediated recombination. In situ hybridization, immunohistochemistry, and quantitative reverse transcriptase-PCR revealed that Dicer is essential for pituitary morphogenesis and correct expression of hormones. Strikingly, αGSU (alpha glycoprotein subunit, common to three pituitary hormones) was absent in Dicer-deleted pituitaries. αGSU mRNA is unstable and its half-life increases during pituitary development. A transcriptome-wide analysis of microdissected E12.5 pituitaries revealed a significant increment of KSRP expression in conditional Dicer-deleted mice. We found that KSRP directly binds to αGSU mRNA, promoting its rapid decay; and, during pituitary development, αGSU expression displays an inverse temporal relationship to KSRP. Further, let-7b/c downregulated KSRP expression, promoting the degradation of its mRNA by directly binding to the 3'UTR. Therefore, we propose a model in which let-7b/c and KSRP operate within a negative feedback loop. Starting from E12.5, KSRP induces the maturation of let-7b/c that, in turn, post-transcriptionally downregulates the expression of KSRP itself. This event leads to stabilization of αGSU mRNA, which ultimately enhances the steady-state expression levels. We have identified a post-transcriptional regulatory network active during mouse pituitary development in which the expression of the hormone αGSU is increased by let7b/c through downregulation of KSRP. Our study unveils a functional crosstalk between miRNA- and AMD-dependent gene regulation during mammalian organogenesis events.
PLoS Genetics 07/2012; 8(7):e1002823. · 8.69 Impact Factor
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ABSTRACT: Central neurons respond to synaptic inputs from other neurons by generating synaptic potentials. Once the summated synaptic potentials reach threshold for action potential firing, the signal propagates leading to transmitter release at the synapse. The calcium influx accompanying such signaling opens calcium-activated ion channels for feedback regulation. Here, we report a mechanism for modulating hippocampal neuronal signaling that involves calcium-activated chloride channels (CaCCs). We present evidence that CaCCs reside in hippocampal neurons and are in close proximity of calcium channels and NMDA receptors to shorten action potential duration, dampen excitatory synaptic potentials, impede temporal summation, and raise the threshold for action potential generation by synaptic potential. Having recently identified TMEM16A and TMEM16B as CaCCs, we further show that TMEM16B but not TMEM16A is important for hippocampal CaCC, laying the groundwork for deciphering the dynamic CaCC modulation of neuronal signaling in neurons important for learning and memory.
Neuron 04/2012; 74(1):179-92. · 14.74 Impact Factor
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ABSTRACT: Myosalpinx contractions are critical for oocyte transport along the oviduct. A specialized population of pacemaker cells-oviduct interstitial cells of Cajal-generate slow waves, the electrical events underlying myosalpinx contractions. The ionic basis of oviduct pacemaker activity is unknown. We examined the role of a new class of Ca(2+)-activated Cl(-) channels (CaCCs)-anoctamin 1, encoded by Tmem16a-in oviduct slow wave generation. RT-PCR revealed the transcriptional expression of Tmem16a-encoded CaCCs in the myosalpinx. Intracellular microelectrode recordings were performed in the presence of two pharmacologically distinct Cl(-) channel antagonists, anthracene-9-carboxylic acid and niflumic acid. Both of these inhibitors caused membrane hyperpolarization, reduced the duration of slow waves, and ultimately inhibited pacemaker activity. Niflumic acid also inhibited propagating calcium waves within the myosalpinx. Slow waves were present at birth in wild-type and heterozygous oviducts but failed to develop by birth in mice homozygous for a null allele of Tmem16a (Tmem16a(tm1Bdh/tm1Bdh)). These data suggest that Tmem16a-encoded CaCCs contribute to membrane potential and are responsible for the upstroke and plateau phases of oviduct slow waves.
Biology of Reproduction 01/2012; 86(1):1-7. · 4.01 Impact Factor
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ABSTRACT: Outgrowth and patterning of the vertebrate limb requires a functional apical ectodermal ridge (AER). The AER is a thickening of ectodermal tissue located at the distal end of the limb bud. Loss of this structure, either through genetic or physical manipulations results in truncation of the limb. A number of genes, including Bmps, are expressed in the AER. Previously, it was shown that removal of the BMP receptor Bmpr1a specifically from the AER resulted in complete loss of hindlimbs suggesting that Bmp signaling in the AER is required for limb outgrowth. In this report, we genetically removed the three known AER-expressed Bmp ligands, Bmp2, Bmp4 and Bmp7 from the AER of the limb bud using floxed conditional alleles and the Msx2-cre allele. Surprisingly, only defects in digit patterning and not limb outgrowth were observed. In triple mutants, the anterior and posterior AER was present but loss of the central region of the AER was observed. These data suggest that Bmp ligands expressed in the AER are not required for limb outgrowth but instead play an essential role in maintaining the AER and patterning vertebrate digits.
PLoS ONE 01/2012; 7(5):e37826. · 4.09 Impact Factor
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ABSTRACT: The vertebrae notochord is a transient rod-like structure that produces secreted factors that are responsible for patterning surrounding tissues. During later mouse embryogenesis, the notochord gives rise to the middle part of the intervertebral disc, called the nucleus pulposus. Currently, very little is known about the molecular mechanisms responsible for forming the intervertebral discs. Here we demonstrate that hedgehog signaling is required for formation of the intervertebral discs. Removal of hedgehog signaling in the notochord and nearby floorplate resulted in the formation of an aberrant notochord sheath that normally surrounds this structure. In the absence of the notochord sheath, small nuclei pulposi were formed, with most notochord cells dispersed throughout the vertebral bodies during embryogenesis. Our data suggest that the formation of the notochord sheath requires hedgehog signaling and that the sheath is essential for maintaining the rod-like structure of the notochord during early embryonic development. As notochord cells form nuclei pulposi, we propose that the notochord sheath functions as a "wrapper" around the notochord to constrain these cells along the vertebral column.
Proceedings of the National Academy of Sciences 06/2011; 108(23):9484-9. · 9.68 Impact Factor
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ABSTRACT: Dicer is an enzyme that processes microRNAs (miRNAs) to their mature forms. As miRNAs were first discovered for their role in the control of developmental timing, we investigated their potential requirement in mouse somitogenesis, an event with precise temporal periodicity. To address the collective role of miRNAs in mesoderm development including somite formation, we used T (Brachyury)-Cre mouse line to inactivate Dicer in most cells of the mesoderm lineage. This Dicer mutant exhibits a reduced anterior-posterior axis. Somite number remains normal in mutant embryos up until the death of the embryos more than two days after Dicer inactivation. Consistent with this, the molecular machineries required for establishing segmentation, including clock and wave front, are not perturbed. However, somite size is reduced and later-formed somites are caudalized, coincident with increased cell death. Outside of the paraxial mesoderm and prior to apparent reduction of the axis in the mutant, the position of the hindlimb bud, a lateral plate mesoderm-derived structure, is posteriorly shifted and the timing of hindlimb bud initiation is delayed accordingly. We observed changes in the expression of genes critical for limb positioning, which include a shifted and delayed downregulation of Hand2 and Tbx3, and shifted and delayed upregulation of Gli3 in the prospective limb bud field. The 3' UTRs of both Hand2 and Tbx3 harbor target sites for a seed sequence-sharing family of miRNAs mir-25/32/92/363/367. As an example of the family we show that mir-363, a miRNA with elevated expression in the prospective limb bud field, is capable of inhibiting Hand2/Tbx3 expression in vitro in a binding site-dependent manner. Together, our findings provide the first demonstration that in mouse embryonic mesoderm, while Dicer is dispensable for somite segmentation, it is essential for proper limb bud positioning.
Developmental Biology 03/2011; 351(2):254-65. · 4.07 Impact Factor
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Brian D Harfe
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ABSTRACT: The vertebrate limb is an excellent model organ system to investigate how signaling pathways interact. Over the last half-century, experiments investigating patterning in the vertebrate limb have led directly to the discovery of many of the molecules and molecular pathways that are not only responsible for limb patterning but the patterning of many different organ systems. In the limb bud, the zone of polarizing activity (ZPA) has long been known to produce factor(s) that are essential for normal limb formation. Recently, one of these factors, Sonic Hedgehog (SHH) was shown to function not only in the limb bud mesenchyme but also in the ectoderm overlying the ZPA. This review discusses the role and potential implications hedgehog signaling in the limb bud ectoderm plays in patterning the vertebrate limb.
Developmental Dynamics 02/2011; 240(5):915-9. · 2.54 Impact Factor
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ABSTRACT: Degeneration of the intervertebral discs, a process characterized by a cascade of cellular, biochemical, structural and functional changes, is strongly implicated as a cause of low back pain. Current treatment strategies for disc degeneration typically address the symptoms of low back pain without treating the underlying cause or restoring mechanical function. A more in-depth understanding of disc degeneration, as well as opportunities for therapeutic intervention, can be obtained by considering aspects of intervertebral disc development. Development of the intervertebral disc involves the coalescence of several different cell types through highly orchestrated and complex molecular interactions. The resulting structures must function synergistically in an environment that is subjected to continuous mechanical perturbation throughout the life of an individual. Early postnatal changes, including altered cellularity, vascular regression and altered extracellular matrix composition, might set the disc on a slow course towards symptomatic degeneration. In this Perspective, we review the pathogenesis and treatment of intervertebral disc degeneration in the context of disc development. Within this scope, we examine how model systems have advanced our understanding of embryonic morphogenesis and associated molecular signaling pathways, in addition to the postnatal changes to the cellular, nutritional and mechanical microenvironment. We also discuss the current status of biological therapeutic strategies that promote disc regeneration and repair, and how lessons from development might provide clues for their refinement.
Disease Models and Mechanisms 01/2011; 4(1):31-41. · 4.94 Impact Factor
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ABSTRACT: The transition of the mouse embryonic notochord into nuclei pulposi was determined ("fate mapped") in vivo in growth and differentiating factor-5 (GDF-5)-null mice using the Shhcre and R26R alleles.
To determine whether abnormal nuclei pulposi formation from the embryonic notochord was responsible for defects present in adult nuclei pulposi of Gdf-5-null mice.
The development, maintenance, and degeneration of the intervertebral disc are not understood. Previously, we demonstrated that all cells in the adult nucleus pulposus of normal mice are derived from the embryonic notochord. Gdf-5-null mice have been reported to contain intervertebral discs in which the nucleus pulposus is abnormal. It is currently unclear if disc defects in Gdf-5-null mice arise during the formation of nuclei pulposi from the notochord during embryogenesis or result from progressive postnatal degeneration of nuclei pulposi.
Gdf-5 messenger RNA expression was examined in the discs of wild-type embryos by RNA in situ hybridization to determine when and where this gene was expressed. To examine nucleus pulposus formation in Gdf-5-null mice, intervertebral discs in which embryonic notochord cells were marked were analyzed in newborn and 24-week-old mice.
Our Gdf-5 messenger RNA in situ experiments determined that this gene is localized to the annulus fibrosus and not the nucleus pulposus in mouse embryos. Notochord fate-mapping experiments revealed that notochord cells in Gdf-5-null mice correctly form nuclei pulposi.
Our data suggest that the defects reported in the nucleus pulposus of adult Gdf-5-null mice do not result from abnormal patterning of the embryonic notochord. The use of mouse alleles to mark cells that produce all cell types that reside in the adult nucleus pulposus will allow for a detailed examination of disc formation in other mouse mutants that have been reported to contain disc defects.
Spine 01/2011; 36(24):E1555-61. · 2.08 Impact Factor
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Developmental Biology 08/2010; 344(1):485. · 4.07 Impact Factor
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ABSTRACT: Expression of Sonic Hedgehog (Shh) in the posterior mesenchyme of the developing limb bud regulates patterning and growth of the developing limb by activation of the Hedgehog (Hh) signaling pathway. Through the analysis of Shh and Hh signaling target genes, it has been shown that activation in the limb bud mesoderm is required for normal limb development to occur. In contrast, it has been stated that Hh signaling in the limb bud ectoderm cannot occur because components of the Hh signaling pathway and Hh target genes have not been found in this tissue. However, recent array-based data identified both the components necessary to activate the Hh signaling pathway and targets of this pathway in the limb bud ectoderm. Using immunohistochemistry and various methods of detection for targets of Hh signaling, we found that SHH protein and targets of Hh signaling are present in the limb bud ectoderm including the apex of the bud. To directly test whether ectodermal Hh signaling was required for normal limb patterning, we removed Smo, an essential component of the Hh signaling pathway, from the apical ectodermal ridge (AER). Loss of functional Hh signaling in the AER resulted in disruption of the normal digit pattern and formation of additional postaxial cartilaginous condensations. These data indicate that contrary to previous accounts, the Hh signaling pathway is present and required in the developing limb AER for normal autopod development.
Proceedings of the National Academy of Sciences 03/2010; 107(12):5489-94. · 9.68 Impact Factor
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ABSTRACT: Activation of an apical Ca(2+)-dependent Cl(-) channel (CaCC) is the rate-limiting step for fluid secretion in many exocrine tissues. Here, we compared the properties of native CaCC in mouse submandibular salivary gland acinar cells to the Ca(2+)-gated Cl(-) currents generated by Tmem16A and Best2, members from two distinct families of Ca(2+)-activated Cl(-) channels found in salivary glands. Heterologous expression of Tmem16A and Best2 transcripts in HEK293 cells produced Ca(2+)-activated Cl(-) currents with time and voltage dependence and inhibitor sensitivity that resembled the Ca(2+)-activated Cl(-) current found in native salivary acinar cells. Best2(-/-) and Tmem16A(-/-) mice were used to further characterize the role of these channels in the exocrine salivary gland. The amplitude and the biophysical footprint of the Ca(2+)-activated Cl(-) current in submandibular gland acinar cells from Best2-deficient mice were the same as in wild type cells. Consistent with this observation, the fluid secretion rate in Best2 null mice was comparable with that in wild type mice. In contrast, submandibular gland acinar cells from Tmem16A(-/-) mice lacked a Ca(2+)-activated Cl(-) current and a Ca(2+)-mobilizing agonist failed to stimulate Cl(-) efflux, requirements for fluid secretion. Furthermore, saliva secretion was abolished by the CaCC inhibitor niflumic acid in wild type and Best2(-/-) mice. Our results demonstrate that both Tmem16A and Best2 generate Ca(2+)-activated Cl(-) current in vitro with similar properties to those expressed in native cells, yet only Tmem16A appears to be a critical component of the acinar Ca(2+)-activated Cl(-) channel complex that is essential for saliva production by the submandibular gland.
Journal of Biological Chemistry 02/2010; 285(17):12990-3001. · 4.77 Impact Factor
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ABSTRACT: Malformations of the external genitalia are among the most common congenital anomalies in humans. The urogenital and anorectal sinuses develop from the embryonic cloaca, and the penis and clitoris develop from the genital tubercle. Within the genital tubercle, the endodermally derived urethral epithelium functions as an organizer and expresses sonic hedgehog (Shh). Shh knockout mice lack external genitalia and have a persistent cloaca. This identified an early requirement for Shh, but precluded analysis of its later role in the genital tubercle. We conducted temporally controlled deletions of Shh and report that Shh is required continuously through the onset of sexual differentiation. Shh function is divisible into two temporal phases; an anogenital phase, during which Shh regulates outgrowth and patterning of the genital tubercle and septation of the cloaca, and a later external genital phase, during which Shh regulates urethral tube closure. Disruption of Shh function during the anogenital phase causes coordinated anorectal and genitourinary malformations, whereas inactivation during the external genital phase causes hypospadias. Shh directs cloacal septation by promoting cell proliferation in adjacent urorectal septum mesenchyme. Additionally, conditional inactivation of smoothened in the genital ectoderm and cloacal/urethral endoderm shows that the ectoderm is a direct target of Shh and is required for urethral tube closure, highlighting a novel role for genital ectoderm in urethragenesis. Identification of the stages during which disruption of Shh results in either isolated or coordinated malformations of anorectal and external genital organs provides a new tool for investigating the etiology of anogenital malformations in humans.
Development 12/2009; 136(23):3949-57. · 6.60 Impact Factor
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ABSTRACT: Calcium-activated chloride channels (CaCC) with similar hallmark features are present in many cell types and mediate important physiological functions including epithelial secretion, sensory signal transduction, and smooth muscle contraction. Having identified TMEM16A of the transmembrane proteins with unknown function (TMEM) 16 family as a CaCC subunit, we have developed antibodies specific for mouse TMEM16A, as evidenced by the absence of immunoreactivity in TMEM16A knockout mice. Here, we show that TMEM16A is located in the apical membranes of epithelial cells in exocrine glands and trachea. In addition, TMEM16A is expressed in airway smooth muscle cells and the smooth muscle cells of reproductive tracts, the oviduct and ductus epididymis. In the gastrointestinal (GI) tract, TMEM16A is absent from smooth muscle cells, but present in the interstitial cells of Cajal (ICC), the pacemaker cells that control smooth muscle contraction. The physiological importance of TMEM16A is underscored by the diminished rhythmic contraction of gastric smooth muscle from TMEM16A knockout mice. The TMEM16A expression pattern established in this study thus provides a roadmap for the analyses of physiological functions of calcium-activated chloride channels that contain TMEM16A subunits.
Proceedings of the National Academy of Sciences 11/2009; 106(50):21413-8. · 9.68 Impact Factor
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ABSTRACT: Interstitial cells of Cajal (ICC) generate pacemaker activity (slow waves) in gastrointestinal (GI) smooth muscles, but the mechanism(s) of pacemaker activity are controversial. Several conductances, such as Ca2+-activated Cl− channels (CaCC) and non-selective cation channels (NSCC) have been suggested to be involved in slow wave depolarization. We investigated the expression and function of a new class of CaCC, anoctamin 1 (ANO1), encoded by Tmem16a, which was discovered to be highly expressed in ICC in a microarray screen. GI muscles express splice variants of the Tmem16a transcript in addition to other paralogues of the Tmem16a family. ANO1 protein is expressed abundantly and specifically in ICC in all regions of the murine, non-human primate (Macaca fascicularis) and human GI tracts. CaCC blocking drugs, niflumic acid and 4,4′-diisothiocyano-2,2′-stillbene-disulfonic acid (DIDS) reduced the frequency and blocked slow waves in murine, primate, human small intestine and stomach in a concentration-dependent manner. Unitary potentials, small stochastic membrane depolarizations thought to underlie slow waves, were insensitive to CaCC blockers. Slow waves failed to develop by birth in mice homozygous for a null allele of Tmem16a (Tmem16atm1Bdh/tm1Bdh) and did not develop subsequent to birth in organ culture, as in wildtype and heterozygous muscles. Loss of function of ANO1 did not inhibit the development of ICC networks that appeared structurally normal as indicated by Kit antibodies. These data demonstrate the fundamental role of ANO1 in the generation of slow waves in GI ICC.
The Journal of Physiology 10/2009; 587(20):4887 - 4904. · 4.72 Impact Factor
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ABSTRACT: Molecular identification of the Ca(2+)-dependent chloride channel TMEM16A (ANO1) provided a fundamental step in understanding Ca(2+)-dependent Cl(-) secretion in epithelia. TMEM16A is an intrinsic constituent of Ca(2+)-dependent Cl(-) channels in cultured epithelia and may control salivary output, but its physiological role in native epithelial tissues remains largely obscure. Here, we demonstrate that Cl(-) secretion in native epithelia activated by Ca(2+)-dependent agonists is missing in mice lacking expression of TMEM16A. Ca(2+)-dependent Cl(-) transport was missing or largely reduced in isolated tracheal and colonic epithelia, as well as hepatocytes and acinar cells from pancreatic and submandibular glands of TMEM16A(-/-) animals. Measurement of particle transport on the surface of tracheas ex vivo indicated largely reduced mucociliary clearance in TMEM16A(-/-) mice. These results clearly demonstrate the broad physiological role of TMEM16A(-/-) for Ca(2+)-dependent Cl(-) secretion and provide the basis for novel treatments in cystic fibrosis, infectious diarrhea, and Sjöegren syndrome.
Journal of Biological Chemistry 09/2009; 284(42):28698-703. · 4.77 Impact Factor
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ABSTRACT: All vertebrate cells regulate their cell volume by activating chloride channels of unknown molecular identity, thereby activating regulatory volume decrease. We show that the Ca(2+)-activated Cl(-) channel TMEM16A together with other TMEM16 proteins are activated by cell swelling through an autocrine mechanism that involves ATP release and binding to purinergic P2Y(2) receptors. TMEM16A channels are activated by ATP through an increase in intracellular Ca(2+) and a Ca(2+)-independent mechanism engaging extracellular-regulated protein kinases (ERK1/2). The ability of epithelial cells to activate a Cl(-) conductance upon cell swelling, and to decrease their cell volume (regulatory volume decrease) was dependent on TMEM16 proteins. Activation of I(Cl,swell) was reduced in the colonic epithelium and in salivary acinar cells from mice lacking expression of TMEM16A. Thus TMEM16 proteins appear to be a crucial component of epithelial volume-regulated Cl(-) channels and may also have a function during proliferation and apoptotic cell death.
Journal of Biological Chemistry 09/2009; 284(42):28571-8. · 4.77 Impact Factor
