Biology subjects

Martinez, M. L.

Publications and source records attributed to Martinez, M. L..

3 recordsLinked to original sources

bioRxiv2024

A role for class I PAKs in the regulation of the excitability of the actin cytoskeleton.

P21 activated kinases (PAKs) are involved in a wide range of functions from the regulation of the cytoskeleton to the control of apoptosis and proliferation. Although many PAK substrates identified are implicated in the regulation of the actin cytoskeleton, a coherent picture of the total effect of PAK activation on the state of the actin cytoskeleton is unclear. We therefore set out to observe and quantify the effect of PAK inhibition on the actin cytoskeleton in greater detail. In Mouse Embryonic Fibroblasts, inhibition of PAK kinase activity, either by treatment with small molecule inhibitors or overexpression of mutant PAK constructs leads to the constitutive production of patches of the phosphoinositide PIP3 on the ventral surface of the cell. The formation of these patches remodels the actin cytoskeleton and polarises the cell. From the overexpression of truncated and mutant PAK constructs as well as an in vitro model of PAK recruitment to small GTPases we propose that this is due to a hyper recruitment of PAK and PAK binding partners in the absence of PAK kinase activity. This aberrant production of PIP3 suggests that, by limiting its own recruitment, the kinase activity of class I PAKs acts to downregulate PI3K activity, further highlighting class I PAKs as regulators of PI3K activity and therefore the excitability of the actin cytoskeleton.

cell biology↗

bioRxiv2021

Encapsulated allografts preclude host sensitization and promote ovarian endocrine function in ovariectomized young rhesus monkeys and sensitized mice

Transplantation of allogeneic donor ovarian tissue holds great potential for female cancer survivors who often experience premature ovarian insufficiency. To avoid complications associated with immune suppression and to protect transplanted ovarian allografts from immune-mediated injury, we have developed an immuno-isolating hydrogel-based capsule that supports the function of ovarian allografts without triggering an immune response. Encapsulated ovarian allografts implanted in naive ovariectomized BALB/c mice responded to the circulating gonadotropins without direct revascularization and maintained function for 4 months, as evident by regular estrous cycles and presence of antral follicles in the retrieved grafts. Repeated implantations of encapsulated mouse ovarian allografts did not sensitize naive BALB/c mice in contrast to non-encapsulated controls, which was confirmed with undetectable levels of allo-antibody. Further, encapsulated allografts implanted in hosts previously sensitized by implantation of non-encapsulated allografts restored estrous cycles similarly to our results in naive recipients. Next, we tested the translational potential and efficiency of the immune-isolating capsule in a rhesus monkey model by implanting encapsulated ovarian auto- and allografts in young ovariectomized animals. The encapsulated ovarian grafts survived and restored basal levels of urinary estrone conjugate and pregnanediol 3-glucuronide during the approximate 4-5 month observation period. We demonstrate, for the first time, that encapsulation of ovarian allografts prevents sensitization and protects the allograft from rejection in young rhesus monkeys and in sensitized mice.

bioengineering↗

bioRxiv2021

Early embryonic loss following intravaginal Zika virus challenge in rhesus macaques

Zika virus (ZIKV) is an arthropod-borne virus (arbovirus) and is primarily transmitted by Aedes species mosquitoes; however, ZIKV can also be sexually transmitted. During the initial epidemic and in places where ZIKV is now considered endemic, it is difficult to disentangle the risks and contributions of sexual versus vector-borne transmission to adverse pregnancy outcomes. To examine the potential impact of sexual transmission of ZIKV on pregnancy outcome, we challenged three rhesus macaques (Macaca mulatta) three times intravaginally with 1 x 107 PFU of a low passage, African lineage ZIKV isolate (ZIKV-DAK) in the first trimester ([~]30 days gestational age). Samples were collected from all animals initially on days 3 through 10 post challenge, followed by twice, and then once weekly sample collection; ultrasound examinations were performed every 3-4 days then weekly as pregnancies progressed. All three dams had ZIKV RNA detectable in plasma on day 3 post-ZIKV challenge. At approximately 45 days gestation (17-18 days post-challenge), two of the three dams were found to have nonviable embryos by ultrasound. Viral RNA was detected in recovered tissues and at the maternal-fetal interface (MFI) in both cases. The remaining viable pregnancy proceeded to near term ([~]155 days gestational age) and ZIKV RNA was detected at the MFI but not in fetal tissues. These results suggest that sexual transmission of ZIKV may represent an underappreciated risk of pregnancy loss during early gestation.

microbiology↗