Biomedical subjects

Mandar M Inamdar

Publications and source records attributed to Mandar M Inamdar.

4 recordsLinked to original sources

PubMed2026

Developmental regulation of progenitor aging shapes long-term intestinal homeostasis in Drosophila.

Aging causes disruption of tissue homeostasis, with stem cell exhaustion as a major hallmark. However, whether aging trajectories are established during development remains unexplored. Here, we demonstrate that genetic modulation of aging-associated pathways in larval adult midgut progenitors (AMPs) determines the trajectory of Drosophila adult intestinal homeostasis. Induction of aging-associated pathways in the AMPs results in aberrant proliferation, skewed differentiation, barrier dysfunction, and genomic instability. Ultimately, AMP islet architecture is destabilized and age-related molecular signatures are altered. In contrast, reversing aging-associated effects results in a decrease in the enteroendocrine population and the barrier is unaffected. Together, our findings demonstrate that aging-associated pathways are tightly regulated during early development and perturbation can hamper adult gut homeostasis, establishing AMPs as key developmental determinants.

Drosophila↗

PubMed2006

Dynamics of DNA ejection from bacteriophage.

The ejection of DNA from a bacterial virus (i.e., phage) into its host cell is a biologically important example of the translocation of a macromolecular chain along its length through a membrane. The simplest mechanism for this motion is diffusion, but in the case of phage ejection a significant driving force derives from the high degree of stress to which the DNA is subjected in the viral capsid. The translocation is further sped up by the ratcheting and entropic forces associated with proteins that bind to the viral DNA in the host cell cytoplasm. We formulate a generalized diffusion equation that includes these various pushing and pulling effects and make estimates of the corresponding speedups in the overall translocation process. Stress in the capsid is the dominant factor throughout early ejection, with the pull due to binding particles taking over at later stages. Confinement effects are also investigated, in the case where the phage injects its DNA into a volume comparable to the capsid size. Our results suggest a series of in vitro experiments involving the ejection of DNA into vesicles filled with varying amounts of binding proteins from phage whose state of stress is controlled by ambient salt conditions or by tuning genome length.

Bacteriophage lambda↗

PubMed2006

The effect of genome length on ejection forces in bacteriophage lambda.

A variety of viruses tightly pack their genetic material into protein capsids that are barely large enough to enclose the genome. In particular, in bacteriophages, forces as high as 60 pN are encountered during packaging and ejection, produced by DNA bending elasticity and self-interactions. The high forces are believed to be important for the ejection process, though the extent of their involvement is not yet clear. As a result, there is a need for quantitative models and experiments that reveal the nature of the forces relevant to DNA ejection. Here, we report measurements of the ejection forces for two different mutants of bacteriophage lambda, lambdab221cI26 and lambdacI60, which differ in genome length by approximately 30%. As expected for a force-driven ejection mechanism, the osmotic pressure at which DNA release is completely inhibited varies with the genome length: we find inhibition pressures of 15 atm and 25 atm, for the short and long genomes, respectively, values that are in agreement with our theoretical calculations.

Bacteriophage lambda↗

PubMed2004

Forces during bacteriophage DNA packaging and ejection.

The conjunction of insights from structural biology, solution biochemistry, genetics, and single-molecule biophysics has provided a renewed impetus for the construction of quantitative models of biological processes. One area that has been a beneficiary of these experimental techniques is the study of viruses. In this article we describe how the insights obtained from such experiments can be utilized to construct physical models of processes in the viral life cycle. We focus on dsDNA bacteriophages and show that the bending elasticity of DNA and its electrostatics in solution can be combined to determine the forces experienced during packaging and ejection of the viral genome. Furthermore, we quantitatively analyze the effect of fluid viscosity and capsid expansion on the forces experienced during packaging. Finally, we present a model for DNA ejection from bacteriophages based on the hypothesis that the energy stored in the tightly packed genome within the capsid leads to its forceful ejection. The predictions of our model can be tested through experiments in vitro where DNA ejection is inhibited by the application of external osmotic pressure.

Bacteriophages↗