Bio


Doctor of Philosophy (Neuroscience) - McGill University (2018)
Bachelor of Technology (Biotechnology) - P.S.G. College of Technology (2010)

Honors & Awards


  • Integrated Program in Neuroscience (IPN) Returning Student Award, IPN, McGill University (2016)
  • IPN GREAT Travel Award, IPN, McGill University (2016)
  • Canadian Association of Neuroscience Travel Award, Canadian Association of Neuroscience (2016)
  • McGill 3M-thesis competition finalist, McGill University (2016)
  • IPN Returning Student Award, IPN, McGill University (2015)
  • Scientifica Imaging Competition - First Prize, Scientifica (2014)
  • IPN Returning Student Award, IPN, McGill University (2013)
  • IPN Recruitment Award, IPN, McGill University (2011)
  • Best Outgoing Student - Biotechnology, P.S.G. College of Technology (2010)

Professional Education


  • Doctor of Philosophy, McGill University (2018)
  • Bachelor of Technology, Psg College Of Technology (2010)

Current Research and Scholarly Interests


Information processing in the oculomotor cerebellum

All Publications


  • Development of Physiological Activity in the Cerebellum Handbook of the Cerebellum and Cerebellar Disorders Jayabal, S., Watt, A. J. Springer, Cham. 2019
  • ATAT1 regulates forebrain development and stress-induced tubulin hyperacetylation. Cellular and molecular life sciences : CMLS Li, L., Jayabal, S., Ghorbani, M., Legault, L. M., McGraw, S., Watt, A. J., Yang, X. J. 2019

    Abstract

    α-Tubulin acetyltransferase 1 (ATAT1) catalyzes acetylation of α-tubulin at lysine 40 in various organisms ranging from Tetrahymena to humans. Despite the importance in mammals suggested by studies of cultured cells, the mouse Atat1 gene is non-essential for survival, raising an intriguing question about its real functions in vivo. To address this question, we systematically analyzed a mouse strain lacking the gene. The analyses revealed that starting at postnatal day 5, the mutant mice display enlarged lateral ventricles in the forebrain, resembling ventricular dilation in human patients with ventriculomegaly. In the mice, ventricular dilation is due to hypoplasia in the septum and striatum. Behavioral tests of the mice uncovered deficits in motor coordination. Birth-dating experiments revealed that neuronal migration to the mutant septum and striatum is impaired during brain development. In the mutant embryonic fibroblasts, we found mild defects in cell proliferation and primary cilium formation. Notably, in these cells, ATAT1 is indispensable for tubulin hyperacetylation in response to high salt, high glucose, and hydrogen peroxide-induced oxidative stress. We investigated the role of ATAT1 in the hematopoietic system using multicolor flow cytometry and found that this system remains normal in the mutant mice. Although tubulin acetylation was undetectable in a majority of mutant tissues, residual levels were detected in the heart, skeletal muscle, trachea, oviduct, thymus and spleen. This study thus not only establishes the importance of ATAT1 in regulating mouse forebrain development and governing tubulin hyperacetylation during stress responses, but also suggests the existence of an additional α-tubulin acetyltransferase.

    View details for DOI 10.1007/s00018-019-03088-3

    View details for PubMedID 30953095

  • Transient cerebellar alterations during development prior to obvious motor phenotype in a mouse model of spinocerebellar ataxia type 6 JOURNAL OF PHYSIOLOGY-LONDON Jayabal, S., Ljungberg, L., Watt, A. J. 2017; 595 (3): 949–66

    Abstract

    Spinocerebellar ataxia type 6 (SCA6) is a midlife-onset neurodegenerative disease caused by a CACNA1A mutation; CACNA1A is also implicated in cerebellar development. We have previously shown that when disease symptoms are present in midlife in SCA684Q/84Q mice, cerebellar Purkinje cells spike with reduced rate and precision. In contrast, we find that during postnatal development (P10-13), SCA684Q/84Q Purkinje cells spike with elevated rate and precision. Although surplus climbing fibres are linked to ataxia in other mouse models, we found surplus climbing fibre inputs on developing (P10-13) SCA684Q/84Q Purkinje cells when motor deficits were not detected. Developmental alterations were transient and were no longer observed in weanling (P21-24) SCA684Q/84Q Purkinje cells. Our results suggest that changes in the developing cerebellar circuit can occur without detectable motor abnormalities, and that changes in cerebellar development may not necessarily persist into adulthood.Although some neurodegenerative diseases are caused by mutations in genes that are known to regulate neuronal development, surprisingly, patients may not present disease symptoms until adulthood. Spinocerebellar ataxia type 6 (SCA6) is one such midlife-onset disorder in which the mutated gene, CACNA1A, is implicated in cerebellar development. We wondered whether changes were observed in the developing cerebellum in SCA6 prior to the detection of motor deficits. To address this question, we used a transgenic mouse with a hyper-expanded triplet repeat (SCA684Q/84Q ) that displays late-onset motor deficits at 7 months, and measured cerebellar Purkinje cell synaptic and intrinsic properties during postnatal development. We found that firing rate and precision were enhanced during postnatal development in P10-13 SCA684Q/84Q Purkinje cells, and observed surplus multiple climbing fibre innervation without changes in inhibitory input or dendritic structure during development. Although excess multiple climbing fibre innervation has been associated with ataxic symptoms in several adult transgenic mice, we observed no detectable changes in cerebellar-related motor behaviour in developing SCA684Q/84Q mice. Interestingly, we found that developmental alterations were transient, as both Purkinje cell firing properties and climbing fibre innervation from weanling-aged (P21-24) SCA684Q/84Q mice were indistinguishable from litter-matched control mice. Our results demonstrate that significant alterations in neuronal circuit development may be observed without any detectable behavioural read-out, and that early changes in brain development may not necessarily persist into adulthood in midlife-onset diseases.

    View details for DOI 10.1113/JP273184

    View details for Web of Science ID 000394582000035

    View details for PubMedID 27531396

    View details for PubMedCentralID PMC5285638

  • Transient Developmental Purkinje Cell Axonal Torpedoes in Healthy and Ataxic Mouse Cerebellum FRONTIERS IN CELLULAR NEUROSCIENCE Ljungberg, L., Lang-Ouellette, D., Yang, A., Jayabal, S., Quilez, S., Watt, A. J. 2016; 10: 248

    Abstract

    Information is carried out of the cerebellar cortical microcircuit via action potentials propagated along Purkinje cell axons. In several human neurodegenerative diseases, focal axonal swellings on Purkinje cells - known as torpedoes - have been associated with Purkinje cell loss. Interestingly, torpedoes are also reported to appear transiently during development in rat cerebellum. The function of Purkinje cell axonal torpedoes in health as well as in disease is poorly understood. We investigated the properties of developmental torpedoes in the postnatal mouse cerebellum of wild-type and transgenic mice. We found that Purkinje cell axonal torpedoes transiently appeared on axons of Purkinje neurons, with the largest number of torpedoes observed at postnatal day 11 (P11). This was after peak developmental apoptosis had occurred, when Purkinje cell counts in a lobule were static, suggesting that most developmental torpedoes appear on axons of neurons that persist into adulthood. We found that developmental torpedoes were not associated with a presynaptic GABAergic marker, indicating that they are not synapses. They were seldom found at axonal collateral branch points, and lacked microglia enrichment, suggesting that they are unlikely to be involved in axonal refinement. Interestingly, we found several differences between developmental torpedoes and disease-related torpedoes: developmental torpedoes occurred largely on myelinated axons, and were not associated with changes in basket cell innervation on their parent soma. Disease-related torpedoes are typically reported to contain neurofilament; while the majority of developmental torpedoes did as well, a fraction of smaller developmental torpedoes did not. These differences indicate that developmental torpedoes may not be functionally identical to disease-related torpedoes. To study this further, we used a mouse model of spinocerebellar ataxia type 6 (SCA6), and found elevated disease-related torpedo number at 2 years. However, we found normal levels of developmental torpedoes in these mice. Our findings suggest that the transient emergence of Purkinje cell axonal torpedoes during the second postnatal week in mice represents a normal morphological feature in the developing cerebellar microcircuit.

    View details for DOI 10.3389/fncel.2016.00248

    View details for Web of Science ID 000386977200001

    View details for PubMedID 27853421

    View details for PubMedCentralID PMC5089982

  • 4-aminopyridine reverses ataxia and cerebellar firing deficiency in a mouse model of spinocerebellar ataxia type 6 SCIENTIFIC REPORTS Jayabal, S., Chang, H., Cullen, K. E., Watt, A. J. 2016; 6: 29489

    Abstract

    Spinocerebellar ataxia type 6 (SCA6) is a devastating midlife-onset autosomal dominant motor control disease with no known treatment. Using a hyper-expanded polyglutamine (84Q) knock-in mouse, we found that cerebellar Purkinje cell firing precision was degraded in heterozygous (SCA6(84Q/+)) mice at 19 months when motor deficits are observed. Similar alterations in firing precision and motor control were observed at disease onset at 7 months in homozygous (SCA6(84Q/84Q)) mice, as well as a reduction in firing rate. We further found that chronic administration of the FDA-approved drug 4-aminopyridine (4-AP), which targets potassium channels, alleviated motor coordination deficits and restored cerebellar Purkinje cell firing precision to wildtype (WT) levels in SCA6(84Q/84Q) mice both in acute slices and in vivo. These results provide a novel therapeutic approach for treating ataxic symptoms associated with SCA6.

    View details for DOI 10.1038/srep29489

    View details for Web of Science ID 000379298000001

    View details for PubMedID 27381005

    View details for PubMedCentralID PMC4933933

  • Rapid Onset of Motor Deficits in a Mouse Model of Spinocerebellar Ataxia Type 6 Precedes Late Cerebellar Degeneration(1,2,3) ENEURO Jayabal, S., Ljungberg, L., Erwes, T., Cormier, A., Quilez, S., El Jaouhari, S., Watt, A. J. 2015; 2 (6)

    Abstract

    Spinocerebellar ataxia type 6 (SCA6) is an autosomal-dominant cerebellar ataxia that has been associated with loss of cerebellar Purkinje cells. Disease onset is typically at midlife, although it can vary widely from late teens to old age in SCA6 patients. Our study focused on an SCA6 knock-in mouse model with a hyper-expanded (84X) CAG repeat expansion that displays midlife-onset motor deficits at ∼7 months old, reminiscent of midlife-onset symptoms in SCA6 patients, although a detailed phenotypic analysis of these mice has not yet been reported. Here, we characterize the onset of motor deficits in SCA6(84Q) mice using a battery of behavioral assays to test for impairments in motor coordination, balance, and gait. We found that these mice performed normally on these assays up to and including at 6 months, but motor impairment was detected at 7 months with all motor coordination assays used, suggesting that motor deficits emerge rapidly during a narrow age window in SCA6(84Q) mice. In contrast to what is seen in SCA6 patients, the decrease in motor coordination was observed without alterations in gait. No loss of cerebellar Purkinje cells or striatal neurons were observed at 7 months, the age at which motor deficits were first detected, but significant Purkinje cell loss was observed in 2-year-old SCA6(84Q) mice, arguing that Purkinje cell death does not significantly contribute to the early stages of SCA6.

    View details for DOI 10.1523/ENEURO.0094-15.2015

    View details for Web of Science ID 000218571500011

    View details for PubMedID 26730403

    View details for PubMedCentralID PMC4697081

  • DNA-mediated cooperativity facilitates the co-selection of cryptic enhancer sequences by SOX2 and PAX6 transcription factors NUCLEIC ACIDS RESEARCH Narasimhan, K., Pillay, S., Huang, Y., Jayabal, S., Udayasuryan, B., Veerapandian, V., Kolatkar, P., Cojocaru, V., Pervushin, K., Jauch, R. 2015; 43 (3): 1513–28

    Abstract

    Sox2 and Pax6 are transcription factors that direct cell fate decision during neurogenesis, yet the mechanism behind how they cooperate on enhancer DNA elements and regulate gene expression is unclear. By systematically interrogating Sox2 and Pax6 interaction on minimal enhancer elements, we found that cooperative DNA recognition relies on combinatorial nucleotide switches and precisely spaced, but cryptic composite DNA motifs. Surprisingly, all tested Sox and Pax paralogs have the capacity to cooperate on such enhancer elements. NMR and molecular modeling reveal very few direct protein-protein interactions between Sox2 and Pax6, suggesting that cooperative binding is mediated by allosteric interactions propagating through DNA structure. Furthermore, we detected and validated several novel sites in the human genome targeted cooperatively by Sox2 and Pax6. Collectively, we demonstrate that Sox-Pax partnerships have the potential to substantially alter DNA target specificities and likely enable the pleiotropic and context-specific action of these cell-lineage specifiers.

    View details for DOI 10.1093/nar/gku1390

    View details for Web of Science ID 000351638000023

    View details for PubMedID 25578969

    View details for PubMedCentralID PMC4330359

  • Neuronal morphometry directly from bitmap images NATURE METHODS Ferreira, T. A., Blackman, A. V., Oyrer, J., Jayabal, S., Chung, A. J., Watt, A. J., Sjoestroem, P., van Meyel, D. J. 2014; 11 (10): 982–84

    View details for DOI 10.1038/nmeth.3125

    View details for Web of Science ID 000342719100005

    View details for PubMedID 25264773

    View details for PubMedCentralID PMC5271921

  • Crystallization and preliminary X-ray diffraction analysis of the Pax9 paired domain bound to a DC5 enhancer DNA element ACTA CRYSTALLOGRAPHICA SECTION F-STRUCTURAL BIOLOGY COMMUNICATIONS Narasimhan, K., Hilbig, A., Udayasuryan, B., Jayabal, S., Kolatkar, P. R., Jauch, R. 2014; 70: 1357–61

    Abstract

    Pax genes belong to a family of metazoan transcription factors that are known to play a critical role in eye, ear, kidney and neural development. The mammalian Pax family of transcription factors is characterized by a ∼128-amino-acid DNA-binding paired domain that makes sequence-specific contacts with DNA. The diversity in Pax gene activities emerges from complex modes of interaction with enhancer regions and heterodimerization with multiple interaction partners. Based on in vitro optimal binding-site selection studies and enhancer identification assays, it has been suggested that Pax proteins may recognize and bind their target DNA elements with different binding modes/topologies, however this hypothesis has not yet been structurally explored. One of the most extensively studied DNA target elements of the Pax6 paired domain is the eye-lens specific DC5 (δ-crystallin) enhancer element. In order to shed light on Pax6-DC5 DNA interactions, the related paired-domain prototype Pax9 was crystallized with the minimal δ-crystallin DC5 enhancer element and preliminary X-ray diffraction analysis was attempted. A 3.0 Å resolution native data set was collected at the National Synchrotron Light Source (NSLS), Brookhaven from crystals grown in a solution consisting of 10%(w/v) PEG 20K, 20%(v/v) PEG 550 MME, 0.03 M NaNO3, 0.03 M Na2HPO4, 0.03 M NH2SO4, 0.1 M MES/imidazole pH 6.5. The data set was indexed and merged in space group C2221, with unit-cell parameters a = 75.74, b = 165.59, c = 70.14 Å, α = β = γ = 90°. The solvent content in the unit cell is consistent with the presence of one Pax9 paired domain bound to duplex DNA in the asymmetric unit.

    View details for DOI 10.1107/S2053230X14017415

    View details for Web of Science ID 000343060200010

    View details for PubMedID 25286939

    View details for PubMedCentralID PMC4188079