Biology subjects

Smith, L. B.

Publications and source records attributed to Smith, L. B..

6 recordsLinked to original sources

bioRxiv2026

Moving through everyday life: distinct developmental timescales for head-rotation magnitude and rotation efficiency in infancy

Infants actively shape their experience through self-generated movement. They need to move their head efficiently to explore and interact with their environment and to hold their head still to sustain attention. Controlled laboratory studies have documented the importance of head movements in orienting and stabilizing infant visual attention, but little is known about how head control develops as infants go about daily life, the setting in which development actually unfolds. We analyzed 383 hours of egocentric video collected from 88 infants aged 3 weeks to 29 months using head-mounted cameras in infants homes. Using a visual-odometry algorithm, we quantified rotational magnitude, the size of head movements; and rotational efficiency, the directional coherence of head movements. Head-rotation magnitude increased across the first year, and rotational efficiency improved throughout development.

neuroscience↗

bioRxiv2022

A Role for Steroid 5 alpha-reductase 1 in Vascular Remodelling During Endometrial Decidualisation

Decidualisation is the hormone-dependent process of endometrial remodelling that is essential for fertility and reproductive health. It is characterised by dynamic changes in the endometrial stromal compartment including differentiation of fibroblasts, immune cell trafficking and vascular remodelling. Deficits in decidualisation are implicated in disorders of pregnancy such as implantation failure, intra-uterine growth restriction, and pre-eclampsia. Androgens are key regulators of decidualisation that promote optimal differentiation of stromal fibroblasts and activation of downstream signalling pathways required for endometrial remodelling. We have shown that androgen biosynthesis, via 5-reductase-dependent production of dihydrotestosterone, is required for optimal decidualisation of human stromal fibroblasts in vitro, but whether this is required for decidualisation in vivo has not been tested. In the current study we used steroid 5-reductase type 1 (SRD5A1) deficient mice (Srd5a1-/- mice) and a validated model of induced decidualisation to investigate the role of SRD5A1 and intracrine androgen signalling in endometrial decidualisation. We measured decidualisation response (weight/proportion), transcriptomic changes, and morphological and functional parameters of vascular development. These investigations revealed a striking effect of 5-reductase deficiency on the decidualisation response. Furthermore, vessel permeability and transcriptional regulation of angiogenesis signalling pathways, particularly those that involved vascular endothelial growth factor (VEGF), were disrupted in the absence of 5-reductase. In Srd5a1-/- mice, injection of dihydrotestosterone co-incident with decidualisation restored decidualisation responses, vessel permeability, and expression of angiogenesis genes to wild type levels. Androgen availability declines with age which may contribute to age-related risk of pregnancy disorders. These findings show that intracrine androgen signalling is required for optimal decidualisation in vivo and confirm a major role for androgens in the development of the vasculature during decidualisation through regulation of the VEGF pathway. These findings highlight new opportunities for improving age-related deficits in fertility and pregnancy health by targeting androgen-dependent signalling in the endometrium.

physiology↗

bioRxiv2021

Specific transcriptomic signatures and dual regulation of steroidogenesis between fetal and adult mouse Leydig cells

Leydig cells (LC) are the main testicular androgen-producing cells. In eutherian mammals, two types of LCs emerge successively during testicular development, fetal Leydig cells (FLCs) and adult Leydig cells (ALCs). Both display significant differences in androgen production and regulation. Using bulk RNA sequencing, we compared the transcriptomes of both LC populations to characterise their specific transcriptional and functional features. Despite similar transcriptomic profiles, a quarter of the genes show significant variations in expression between FLCs and ALCs. Non-transcriptional events, such as alternative splicing was also observed, including a high rate of intron retention in FLCs compared to ALCs. The use of single-cell RNA sequencing data also allowed the identification of nine FLC-specific genes and 50 ALC-specific genes. Expression of the corticotropin-releasing hormone 1 (Crhr1) receptor and the ACTH receptor melanocortin type 2 receptor (Mc2r) specifically in FLCs suggests a dual regulation of steroidogenesis. The androstenedione synthesis by FLCs is stimulated by luteinizing hormone (LH), CRH and ACTH whereas the testosterone synthesis by ALCs is dependent exclusively on LH. Overall, our study provides a useful database to explore LC development and function.

developmental biology↗

bioRxiv2020

Hyperprolactinemia in a male pituitary androgen receptor knockout mouse model is associated with a female-like pattern of lactotroph development

Circulating prolactin concentration in rodents and humans is sexually dimorphic. Estrogens are a well-characterised stimulator of prolactin release. Circulating prolactin fluctuates throughout the menstrual/estrous cycle of females in response to estrogen levels, but remains continually low in males. We have previously identified androgens as an inhibitor of prolactin release through characterisation of males of a mouse line with a conditional pituitary androgen receptor knockout (PARKO) which have an increase in circulating prolactin, but unchanged lactotroph number. In the present study we aimed to specify the cell type that androgens act on to repress prolactin release. We examined lactotroph-specific, Pit1 lineage-specific and neural-specific conditional AR knockouts, however they did not duplicate the high circulating prolactin seen in the pituitary androgen receptor knockout line, suggesting that the site of androgen repression of prolactin production was another cell type. Using electron microscopy to examine ultrastructure we showed that pituitary androgen receptor knockout male mice develop lactotrophs that resemble those seen in female mice, and that this is likely to contribute to the increase in circulating prolactin. When castrated, pituitary androgen receptor knockout males have significantly reduced circulating prolactin compared to intact males, which suggests that removal of circulating estrogens as well as androgens reduces the stimulation of pituitary prolactin release. However, when expression of selected estrogen-regulated anterior pituitary genes were examined there were no differences in expression level between controls and knockouts. Further investigation is needed into prolactin regulation by changes in androgen-estrogen balance, which has implications not only in the normal sexual dimorphism of physiology but also in diseases such as hyperprolactinemia.

physiology↗

bioRxiv2020

Ectopic FGF23 production induces mineral changes, osteogenic transdifferentiation, and cancer associated microcalcifications

Testicular microcalcifications consist of hydroxyapatite and have been associated with an increased risk of testicular germ cell tumors (TGCTs) but are also found in benign cases such as loss-of-function variants in the phosphate-transporter SLC34A2. Here, we show that fibroblast growth factor 23 (FGF23), a regulator of phosphate homeostasis, is expressed in testicular germ cell neoplasia in situ (GCNIS), embryonal carcinoma (EC), and human embryonic stem cells. FGF23 is not glycosylated in TGCTs and therefore cleaved into a C-terminal fragment which competitively antagonizes full-length FGF23. Here, Fgf23 knockout mice presented with marked calcifications in the epididymis, spermatogenic arrest, and focally germ cells expressing the osteoblast marker Osteocalcin (gene name: BGLAP, protein name: Osteocalcin). Moreover, the frequent testicular microcalcifications in mice with no functional androgen receptor and lack of circulating gonadotropins are associated with lower Slc34a2 and higher Bglap/Slc34a1 (protein name: NPT2a) expression compared with wild-type mice. In accordance, human testicular specimens with microcalcifications also have lower SLC34A2 and a subpopulation of germ cells express phosphate-transporter NPT2a, Osteocalcin, and RUNX2 highlighting aberrant local phosphate handling and expression of bone-specific proteins. Mineral disturbance in vitro using calcium or phosphate treatment induced deposition of calcium-phosphate in a spermatogonial cell line and this effect was fully rescued by the mineralization-inhibitor pyrophosphate. In conclusion, testicular microcalcifications arise secondary to local alterations in mineral homeostasis, which in combination with impaired Sertoli cell function and reduced levels of mineralization-inhibitors due to high alkaline phosphatase activity in GCNIS and TGCTs, facilitate osteogenic-like differentiation of testicular cells and deposition of hydroxyapatite.

molecular biology↗

bioRxiv2017

Deciphering cell lineage specification during male sex determination with single-cell RNA sequencing

The gonad is a unique biological system for studying cell fate decisions. However, major questions remain regarding the identity of somatic progenitor cells and the transcriptional events driving cell differentiation. Using time course single cell RNA sequencing on XY mouse gonads during sex determination, we identified a single population of somatic progenitor cells prior sex determination. A subset of these progenitors differentiate into Sertoli cells, a process characterized by a highly dynamic genetic program consisting of sequential waves of gene expression. Another subset of multipotent cells maintains their progenitor state but undergo significant transcriptional changes that restrict their competence towards a steroidogenic fate required for the differentiation of fetal Leydig cells. These results question the dogma of the existence of two distinct somatic cell lineages at the onset of sex determination and propose a new model of lineage specification from a unique progenitor cell population.

developmental biology↗