Biology subjects

Mandal, M.

Publications and source records attributed to Mandal, M..

3 recordsLinked to original sources

bioRxiv2018

Ddx3x regulates B-cell development and light chain recombination in mice

The X chromosome gene, DDX3X, is an ATP-dependent RNA helicase with roles in transcription, splicing, nuclear export, and translation. Loss of function mutations in DDX3X are linked to a variety of neoplasms, including B-cell lymphoma. We find that conditional homozygous deletion (Mb1-Cre) of Ddx3x in developing mouse B cells in female mice results in a complete absence of mature peripheral B cells associated with an absolute block at the pro-B cell stage of development in the bone marrow. In male mice with Vav1-Cre or Mb1-Cre mediated hemizygous deletion of Ddx3x, there are less severe reductions in peripheral B-cell frequencies with skewing towards the marginal zone lineage, suggesting that the Y chromosome homolog Ddx3y or other male factors may partially compensate for loss of Ddx3x. Loss of Ddx3x in male mice is associated with perturbations at developmental time points linked to cell cycle arrest and immunoglobulin chain rearrangement. Mechanistically, loss of Ddx3x in pre-B cells is associated with reduced expression of the histone reader Brwd1, failure to curtail proliferation, and defective Igk rearrangement, which skews the peripheral B cell receptor repertoire toward lambda light chain usage. These data reveal that Ddx3x plays an essential role in B-cell development by supporting proliferative and epigenetic changes necessary for rearrangement of immunoglobulin genes.

immunology↗

bioRxiv2017

B-1a cells acquire their unique characteristics by bypassing the pre-BCR selection stage

B-1a cells are long-lived, self-renewing innate like B cells that predominantly inhabit the peritoneal and pleural cavities. In contrast to conventional B-2 cells they have a receptor repertoire that is biased towards bacterial and self-antigens, promoting a rapid response to infection and clearing of apoptotic cells. Although B-1a cells are known to primarily originate from fetal tissues the mechanisms by which they arise has been a topic of debate for many years. Here we show that in the fetal liver (FL) versus bone marrow (BM) environment, reduced IL-7R/STAT5 levels promote immunoglobulin kappa (Igk) recombination at the early pro-B cell stage. As a result, B cells can directly generate a mature B cell receptor (BCR) and bypass the requirement for a pre-BCR and pairing with surrogate light chain (SLC). This alternate pathway of development enables the production of B cells with self reactive, skewed specificity receptors that are peculiar to the B-1a compartment. Together our findings connect seemingly opposing models of B-1a cell development and explain how these cells acquire their unique properties.

immunology↗

bioRxiv2017

Optical Coherence Tomography Reveals Mechanobiologically Stable Self-Organizing Di-Fork Architecture of Mice Cutaneous Scars

Scientific studies report crucial impacts of biomechanical effectors to modulate wound healing either by scarring or regeneration. Further, the biological decision to predominantly favor the former is still cryptic. Real-time visualization of biomechanical manifestations in situ in scarring is hence necessary. Endorsed by nanostructural testing, synthetic phantom analysis, and computational simulations, we found strong mechanobiological correlates for Swept Source Optical Coherence Tomography (SS-OCT) speckles in mice cutaneous repair (full-thickness) up to 10 months. The theoretical basis of the optomechanics to provide insights into scar form-factor and evolution is proposed. Optomechanical changes have been considered as the resultant of intrinsic (e.g. fiber elastic modulus) and gross tissue mechanics (extracellular matrix (ECM)) in maturing scars. Non-invasive optomechanics supported with microscopic findings reveal scars cross-sectional self-organizing di-fork architecture. Dual-compartment heterogeneity of di-fork exhibits stress-evading features with a dichotomy in inhabitant cellular stress-fiber distributions. This differential interactivity of scar with adjoining tissues reflects its architectural intelligence to compensate tissue loss (hypodermis/muscle) by assembling into a di-fork. Gradual establishment of baseline shifted lasting mechanobiological steady-state, later in scarring, expose scar as an alternate stable state within the skin. Significance StatementWound repair in mammals, predominantly culminates into function compromising scar that is occasionally fatal in vital organs. How the biological system often adopts scarring over a restorative regeneration is yet a conundrum. Wound and ambient mechanics play a pivotal role in deciding the healing fate. SS-OCT is hence demonstrated here as a non-invasive window to such mechanical manifestations during skin wound healing. This exposed gradual emergence of temporally maintained and stress-resilient di-fork architecture of the scar with differential neighborhood interfaces. Accommodation of such an alternate self-organizing steady-state of scar sheds light on its sustenance and paradoxical selection.

biophysics↗