The Role of PLAG1 in Mouse Brain Development and Neurogenesis.

The pleomorphic adenoma gene 1 (Plag1) is a transcription factor involved in the regulation of growth and cellular proliferation. Here, we report the spatial distribution and functional implications of PLAG1 expression in the adult mouse brain. We identified Plag1 promoter-dependent ß-galactosidase expression in various brain structures, including the hippocampus, cortex, choroid plexus, subcommisural organ, ependymal cells lining the third ventricle, medial and lateral habenulae and amygdala. We noted striking spatial-restriction of PLAG1 within the cornu ammonis (CA1) region of the hippocampus and layer-specific cortical expression, with abundant expression noted in all layers except layer 5. Furthermore, our study delved into the role of PLAG1 in neurodevelopment, focusing on its impact on neural stem/progenitor cell proliferation. Loss of Plag1 resulted in reduced proliferation and decreased production of neocortical progenitors in vivo, although ex vivo neurosphere experiments revealed no cell-intrinsic defects in the proliferative or neurogenic capacity of Plag1-deficient neural progenitors. Lastly, we explored potential target genes of PLAG1 in the cortex, identifying that Neurogenin 2 (Ngn2) was significantly downregulated in Plag1-deficient mice. In summary, our study provides novel insights into the spatial distribution of PLAG1 expression in the adult mouse brain and its potential role in neurodevelopment. These findings expand our understanding of the functional significance of PLAG1 within the brain, with potential implications for neurodevelopmental disorders and therapeutic interventions.

Grainyhead-like (Grhl) Target Genes in Development and Cancer.

Grainyhead-like (GRHL) factors are essential, highly conserved transcription factors (TFs) that regulate processes common to both natural cellular behaviours during embryogenesis, and de-regulation of growth and survival pathways in cancer. Serving to drive the transcription, and therefore activation of multiple co-ordinating pathways, the three GRHL family members (GRHL1-3) are a critical conduit for modulating the molecular landscape that guides cellular decision-making processes during proliferation, epithelial-mesenchymal transition (EMT) and migration. Animal models and in vitro approaches harbouring GRHL loss or gain-of-function are key research tools to understanding gene function, which gives confidence that resultant phenotypes and cellular behaviours may be translatable to humans. Critically, identifying and characterising the target genes to which these factors bind is also essential, as they allow us to discover and understand novel genetic pathways that could ultimately be used as targets for disease diagnosis, drug discovery and therapeutic strategies. GRHL1-3 and their transcriptional targets have been shown to drive comparable cellular processes in Drosophila, C. elegans, zebrafish and mice, and have recently also been implicated in the aetiology and/or progression of a number of human congenital disorders and cancers of epithelial origin. In this review, we will summarise the state of knowledge pertaining to the role of the GRHL family target genes in both development and cancer, primarily through understanding the genetic pathways transcriptionally regulated by these factors across disparate disease contexts.

Effect of Pleomorphic Adenoma Gene 1 Deficiency on Selected Behaviours in Adult Mice.

The proto-oncogene pleomorphic adenoma gene 1 (Plag1) encodes a zinc finger transcription factor. PLAG1 is part of the high motility group AT hook-2 (HGMA2)-PLAG1-insulin-like growth factor 2 (IGF2) pathway that, when disrupted, leads to Silver-Russell syndrome, a severe form of intrauterine growth restriction. With little known about PLAG1's role in normal physiology, this study is the first to characterise the behavioural phenotype of PLAG1-deficient mice. Mice were tested for differences in circadian locomotor activity and body temperature, sleep-like behaviour, anxiety-like behaviour, cognition, social behaviour, and sensorimotor gating. Overall, the behavioural phenotype of the Plag1 knock-out (KO) mice was mild: no significant differences were seen in circadian activity levels, locomotion, object recognition, spatial memory or sociability compared to wild-type mice. However, the cued test of fear conditioning, prepulse inhibition of the startle response and Preyer's reflex test suggest that Plag1 KO mice may have a hearing impairment. This implies that PLAG1 plays an important role in proper functioning and/or development of the neural circuitry behind the auditory processes or interacts with genes involved in those processes.

Transcriptome analysis of the epididymis from Plag1 deficient mice suggests dysregulation of sperm maturation and extracellular matrix genes.

BACKGROUND: The transcription factor pleomorphic adenoma gene 1 (PLAG1) is required for male fertility. Mice deficient in PLAG1 exhibit decreased sperm motility and abnormal epididymal tubule elongation and coiling, indicating impaired sperm maturation during epididymal transit. However, the downstream transcriptomic profile of the Plag1 knockout (KO; Plag1-/- ) murine epididymis is currently unknown. RESULTS: In this study, the PLAG1-dependent epididymal transcriptome was characterised using RNA sequencing. Several genes important for the control of sperm maturation, motility, capacitation and the acrosome reaction were dysregulated in Plag1-/- mice. Surprisingly, several cell proliferation genes were upregulated, and Ki67 analysis indicated that cell proliferation is aberrantly upregulated in the cauda epididymis stroma of Plag1-/- mice. Gene ontology analysis showed an overall upregulation of genes encoding extracellular matrix components, and an overall downregulation of genes encoding metalloendopeptidases in the epididymides from Plag1-/- mice. CONCLUSION: Together, these results suggest a defect in the epididymal extracellular matrix in Plag1-/- mice. These results imply that in addition to maintaining epididymal integrity directly, PLAG1 may also regulate several genes involved in the regulation of sperm maturation and capacitation. Moreover, PLAG1 may also be involved in regulating tissue homeostasis and ensuring proper structure and maintenance of the extracellular matrix in the epididymis.

Deficiency of the transcription factor PLAG1 results in aberrant coiling and morphology of the epididymis.

Mice deficient in the transcription factor pleomorphic adenoma gene 1 (PLAG1) exhibit reproductive issues that are characterized, in part, by decreased progressive sperm motility in the male. However, the underlying cause of this impairment is unknown. As epididymal transit is critical for sperm maturation and motility, the morphology of the epididymis of Plag1-deficient mice was investigated and the spatial expression patterns of PLAG1 protein and mRNA were identified. Using X-gal staining and in situ hybridization, PLAG1 was shown to be widely expressed in both the epithelium and stroma in all regions of the mouse epididymis. Interestingly, the X-gal staining pattern was markedly different in the cauda, where it could be suggestive of PLAG1 secretion into the epididymal lumen. At all ages investigated, the morphology of epididymides from Plag1 knockout (KO) mice was aberrant; the tubule failed to elongate and coil, particularly in the corpus and cauda, and the cauda was malformed, lacking its usual bulbous shape. Moreover, the epididymides from Plag1 KO mice were significantly reduced in size relative to body weight. In 20% of Plag1-deficient mice, the left testicle and epididymis were lacking. The impaired morphogenesis of the epididymal tubule is likely to be a major contributing factor to the fertility problems observed in male Plag1-deficient mice. These results also establish PLAG1 as an important regulator of male reproduction, not only through its involvement in testicular sperm production, but also via its role in the development and function of the epididymis.

PLAG1 expression and target genes in the hypothalamo-pituitary system in male mice.

Knockout of pleomorphic adenoma gene 1 (PLAG1) in mice results in reduced fertility. To investigate whether PLAG1 is involved in reproductive control by the hypothalamo-pituitary system in males, we determined PLAG1 expression sites and compared gene expression between hypothalami and pituitary glands from Plag1 knockout and wildtype animals. Abundant expression of PLAG1 was detected throughout the pituitary gland, including gonadotropes and somatotropes. The hypothalamus also contained a large number of PLAG1-expressing cells. PLAG1 was expressed in some gonadotropin-releasing hormone neurons, but not in kisspeptin neurons. Gene ontology analysis indicated upregulation of cell proliferation in both structures, and of cholesterol biosynthesis in the hypothalamus, but functional confirmation is required. Expression levels of pituitary gonadotropins and gonadotropin-releasing hormone receptor, and of brain gonadotropin-releasing hormone and kisspeptin mRNA were unaffected in knockout mice. We conclude that PLAG1 deficiency does not have a major impact on the reproductive control by the hypothalamo-pituitary system.