@article {78005, title = {Modulation of β-catenin levels regulates cranial neural crest patterning and dispersal into first pharyngeal arch.}, journal = {Dev Dyn}, year = {2020}, month = {2020 May 19}, abstract = {

BACKGROUND: Vertebrate cranial neural crest cells (CNCCs) are multipotent, proximal to the source CNCC form the cranial ganglia. Distally, in the pharyngeal arches, they give rise to the craniofacial skeleton and connective tissues. Fate choices are made as CNCC pattern into distinct destination compartments. In spite of this importance, the mechanism patterning CNCC is poorly defined.

RESULTS: Here, we report that a novel β-catenin-dependent regulation of N-Cadherin levels may drive CNCC patterning. In mouse embryos, at the first pharyngeal arch axial level, membrane β-catenin levels correlate with the extent of N-cadherin-mediated adhesion and thus suggest the presence of collective and dispersed states of CNCC. Using in vitro human neural crest model and chemical modulators of β-catenin levels, we show a requirement for down-modulating β-catenin for regulating N-cadherin levels and cell-cell adhesion. Similarly, in β-catenin gain-of-function mutant mouse embryos, CNCC fail to lower N-cadherin levels. This indicates a failure to reduce cell-cell adhesion, which may underlie the failure of mutant CNCC to populate first pharyngeal arch.

CONCLUSION: We suggest that β-catenin-mediated regulation of CNCC adhesion, a previously underappreciated mechanism, underlies the patterning of CNCC into fate-specific compartments.

}, issn = {1097-0177}, doi = {10.1002/dvdy.208}, author = {Javali, Alok and Lakshmanan, Vairavan and Palakodeti, Dasaradhi and Sambasivan, Ramkumar} } @article {43840, title = {Divergent early mesoderm specification underlies distinct head and trunk muscle programmes in vertebrates.}, journal = {Development}, volume = {145}, year = {2018}, month = {2018 Sep 20}, abstract = {

Head and trunk muscles have discrete embryological origins and are governed by distinct regulatory programmes. Whereas the developmental route of trunk muscles from mesoderm is well studied, that of head muscles is ill defined. Here, we show that, unlike the myogenic trunk paraxial mesoderm, head mesoderm development is independent of the T/Tbx6 network in mouse. We reveal that, in contrast to Wnt and FGF-driven trunk mesoderm, dual inhibition of Wnt/β-catenin and Nodal specifies head mesoderm. Remarkably, the progenitors derived from embryonic stem cells by dual inhibition efficiently differentiate into cardiac and skeletal muscle cells. This twin potential is the defining feature of cardiopharyngeal mesoderm: the head subtype giving rise to heart and branchiomeric head muscles. Therefore, our findings provide compelling evidence that dual inhibition specifies head mesoderm and unravel the mechanism that diversifies head and trunk muscle programmes during early mesoderm fate commitment. Significantly, this is the first report of directed differentiation of pluripotent stem cells, without transgenes, into progenitors with muscle/heart dual potential. Ability to generate branchiomeric muscle could catalyse efforts in modelling myopathies that selectively involve head muscles.

}, issn = {1477-9129}, doi = {10.1242/dev.160945}, author = {Nandkishore, Nitya and Vyas, Bhakti and Javali, Alok and Ghosh, Subho and Sambasivan, Ramkumar} } @article {45929, title = {Infectivity of adeno-associated virus serotypes in mouse testis.}, journal = {BMC Biotechnol}, volume = {18}, year = {2018}, month = {2018 Nov 01}, pages = {70}, abstract = {

BACKGROUND: Recombinant adeno-associated viruses (AAVs) are emerging as favoured transgene delivery vectors for both research applications and gene therapy. In this context, a thorough investigation of the potential of various AAV serotypes to transduce specific cell types is valuable. Here, we rigorously tested the infectivity of a number of AAV serotypes in murine testis by direct testicular injection.

RESULTS: We report the tropism of serotypes AAV2, 5, 8, 9 and AAVrh10 in mouse testis. We reveal unique infectivity of AAV2 and AAV9, which preferentially target intertubular testosterone-producing Leydig cells. Remarkably, AAV2 TM, a mutant for capsid designed to increase transduction, displayed a dramatic alteration in tropism; it infiltrated seminiferous tubules unlike wildtype AAV2 and transduced Sertoli cells. However, none of the AAVs tested infected spermatogonial cells.

CONCLUSIONS: In spite of direct testicular injection, none of the tested AAVs appeared to infect sperm progenitors as assayed by reporter expression. This lends support to the current view that AAVs are safe gene-therapy vehicles. However, testing the presence of rAAV genomic DNA in germ cells is necessary to assess the risk of individual serotypes.

}, issn = {1472-6750}, doi = {10.1186/s12896-018-0479-1}, author = {Rajasekaran, Santhanasabapathy and Thatte, Jayashree and Periasamy, Jayaprakash and Javali, Alok and Jayaram, Manjunath and Sen, Dwaipayan and Krishnagopal, Akshaya and Jayandharan, Giridhara R and Sambasivan, Ramkumar} } @article {25249, title = {Co-expression of Tbx6 and Sox2 identifies a novel transient neuromesoderm progenitor cell state.}, journal = {Development}, year = {2017}, month = {2017 Oct 30}, abstract = {

The elongation of body axis during development is a key aspect of body plan. Bi-potential neuromesoderm progenitors (NMPs) ensure the axial growth of embryos by contributing both to the spinal cord and mesoderm. The current model for the mechanism controlling NMP deployment invokes Tbx6, a T-box factor, to drive mesoderm differentiation of NMPs. Here, we identify a new population of Tbx6+ cells in a subdomain of NMP niche in mouse embryos. Based on co-expression of a progenitor marker Sox2, we identify this population to represent a transient cell state in the mesoderm-fated NMP lineage. Genetic lineage tracing confirms the presence of Tbx6+ NMP cell state. Furthermore, we report a novel aspect of documented Tbx6 mutant phenotype, i.e., an increase from two to four ectopic neural tubes, corresponding to the switch in NMP niche, highlighting the importance of Tbx6 function in NMP fate decision. This study emphasizes the function of Tbx6 as the bi-stable switch turning mesoderm fate "on" and progenitor state "off", and thus, has implications for the molecular mechanism driving NMP fate choice.

}, issn = {1477-9129}, doi = {10.1242/dev.153262}, author = {Javali, Alok and Misra, Aritra and Leonavicius, Karolis and Acharya, Debalina and Vyas, Bhakti and Sambasivan, Ramkumar} }