Investigating the role of PABPC5 in mouse physiology

Poly(A)-binding proteins (PABPs) are a family of RNA-binding proteins involved in post-transcriptional regulation. In mammals five PABPs have been identified, some widely expressed (e.g., PABP1 and PABP4) while others are limited to specific tissues and developmental time points (e.g., ePABP). The best described member, PABP1, has been found to be essential for the translation of messenger RNA to protein according to in vitro data. However, there is limited literature characterising the role of PABPs in mammalian physiology. PABP5 is another member of the PABP family. It is mammalian-specific, and it is structurally different to other PABPs, but little is known about its function. PABP5 resides in the gene-poor region of Xq21.3 and published data has identified a patient with premature ovarian insufficiency (POI) carrying a deletion in this region, suggesting a possible link between POI and PABP5. Premature ovarian insufficiency is characterised by the reduction and loss of normal ovarian function and affects approximately 1% of women under the age of 40. The genetic basis of POI is complex and poorly understood, necessitating further research into the molecular mechanisms of the condition. Previous work carried out in the lab has shown that Pabp5 is expressed in the granulosa cells of mouse ovaries. Granulosa cells are somatic cells that are key for sex steroid and growth factor production required for follicle development. This implies a role for PABP5 in ovarian function. The aim of this project was to investigate the possible role of PABP5 in murine physiology by creating and characterising a Pabp5 knock-out mouse line, with a primary focus on reproductive health. First, it was established that Pabp5 knock-out mice survive embryonic development and mice of both sexes survive to adulthood. Male and female mice lacking Pabp5 broadly underwent normal development to adulthood: they gained weight at the same rate as wild type animals and no deviations in the necropsy weight of six major organs was observed. In males, gross morphology of four of these organs showed no changes. However, there were possible signs of extramedullary haematopoiesis (EMH) taking place in the liver and spleen. In females, these were observed only in the liver. Cell blood count data from male mice showed a decreased number of circulating erythrocytes and decreased levels of haemoglobin. Trends indicating possible decrease in mean cell haemoglobin concentration, increase in mean corpuscular volume, and increase in red blood cell distribution were also observed. Pilot cell blood count data from female mice did not show any discernible trends. Second, an immune phenotype that emerged during the initial characterisation of Pabp5 knock-out male mice was briefly explored. Male mice lacking Pabp5 exhibited a global decrease in the number of circulating white blood cells. The number of lymphocytes and eosinophils was reduced, while the number of neutrophils was increased. Pilot flow cytometry data did not reveal any trends in the immune cell profile of whole blood, bone marrow, thymus, spleen, small intestine and lymph nodes. Lastly, the reproductive function of Pabp5-deficient male and female mice was investigated. No deviations in reproductive organ morphology and functions were observed in male knock-out mice. Two cohorts of adult female mice aged 12 and 24 weeks were characterised. At 12 weeks, Pabp5 knock-out females exhibited normal ovarian weight, with no deviations in gross ovarian morphology and follicle development. A larger proportion of knock-out mice exhibited an irregular oestrous cycle. No changes in levels of LH, FSH, and progesterone were observed. At 24 weeks, female Pabp5 knock-out mice also exhibited no changes in body and ovary weight. No gross morphological differences were noted, nor was general follicular development affected. However, when follicle health was characterised, an increase in the number of preovulatory follicles with unhealthy granulosa cells was observed. In addition, their oestrous cycle was affected, with more knock-out mice having an irregular cycle and some of these mice spending a longer time in diestrus compared to wild type counterparts. Although serum LH and FSH levels were not affected, a possible decrease in progesterone levels was seen. There was a potential decrease in the number of corpora lutea, and there were fewer MII oocytes following superovulation. First litter fecundity remained unaffected. In conclusion, PABP5 is not essential for development and survival of mice into adulthood but might play a role in female reproductive function later in life, as well as in immune function. However, further study is required to gain more insight into these phenotypes.

Grantor dc:publisher

The University of Edinburgh

Year dc:date.issued

2024

Author dc:creator

• Gyurova, Hristina Dochkova

Advisors dc:contributor.advisor

• Gray, Niki
• Brook, Matthew

• PABPC5
• mouse physiology
• Poly(A)-binding proteins (PABPs)
• RNA-binding proteins
• PABP5
• premature ovarian insufficiency (POI)
• granulosa cells of mouse ovaries
• Granulosa cells
• extramedullary haematopoiesis (EMH)

Language dc:language.iso

en

Identifier URI

http://dx.doi.org/10.7488/era/4570

OAI identifier oai:identifier

oai:era.ed.ac.uk:1842/41847