Biology subjects

Kliman, H. J.

Publications and source records attributed to Kliman, H. J..

4 recordsLinked to original sources

bioRxiv2025

Detection of serotonin and serotonin related gene reveals unique roles in human intestinal epithelial development

Although 95% of serotonin in the human body is produced in the gastrointestinal tract, most prior research work has focused on the brain. Despite its abundance in the gut, serotonins role in early intestinal development remains poorly understood. Here we show that serotonin is detected in both the small intestine and large intestine as early as 14-15 weeks gestational age. Using single-cell transcriptomics with histological validation, we generated a spatiotemporal atlas of serotonin and serotonin-related genes in the human gut from first trimester to late adulthood. The serotonin synthesis gene, TPH1, was exclusively expressed in enteroendocrine cells at all time points analyzed, with the highest expression in the second trimester. The serotonin reuptake gene, SLC6A4, was largely restricted to mature absorptive enterocytes and increased post-natally. Serotonin receptors also displayed distinct cellular and developmental expression patterns. HTR1E was confined to the first trimester during highly proliferative stage. HTR4 was enriched for in crypt regions, suggesting a role in proliferation for serotonin. Finally, HTR3E was associated with tuft cells throughout development. Together, these findings reveal the dynamic, cell-type-specific regulation of serotonin in the developing human gut, suggesting its importance in early intestinal development, and provide a framework to study its roles in intestinal development and diseases.

developmental biology↗

bioRxiv2022

Sex differences in early and term placenta are conserved in adult tissues

BackgroundPregnancy complications vary based on the fetuss genetic sex, which may, in part, be modulated by the placenta. Further, developmental differences early in life can have lifelong health outcomes. Yet, sex differences in gene expression within the placenta at different time points throughout pregnancy and comparisons to adult tissues remains poorly characterized. MethodsHere, we collect and characterize sex differences in gene expression in term placentas ( [≥] 36.6 weeks; 23 male XY and 27 female XX). These are compared with sex differences in previously collected first trimester placenta samples and 42 non-reproductive adult tissues from GTEx. ResultsWe identify 268 and 53 sex differentially expressed genes in the uncomplicated late first trimester and term placentas, respectively. Of the 53 sex differentially expressed genes observed in the term placentas, 31 are also sex differentially expressed genes in the late first trimester placentas. Furthermore, sex differences in gene expression in term placentas are highly correlated with sex differences in the late first trimester placentas. We found that sex differential gene expression in the term placenta is significantly correlated with sex differences in gene expression in 42 non-reproductive adult tissues (correlation coefficient ranged from 0.892 to 0.957), with the highest correlation in brain tissues. Sex differences in gene expression were largely driven by gene expression on the sex chromosomes. We further show that some gametologous genes (genes with functional copies on X and Y) will have different inferred sex differences if the X-linked gene expression in females is compared to the sum of the X-linked and Y-linked gene expression in males. ConclusionsWe find that sex differences in gene expression are conserved in late first trimester and term placentas and that these sex differences are conserved in adult tissues. We demonstrate that there are sex differences associated with innate immune response in late first trimester placentas but there is no significant difference in gene expression of innate immune genes between sexes in healthy full term placentas. Finally, sex differences are predominantly driven by expression from sex-linked genes. HighlightsO_LISex differences in gene expression in late first trimester placentas are positively correlated with sex differences in gene expression in full term placentas; sex differences develop early and are maintained. C_LIO_LISex differences in gene expression on the sex chromosomes in the placenta are correlated to sex differences in adult tissues. C_LIO_LISex-linked gametolog genes require additional methodological approaches for accurate quantification. C_LI

genomics↗

bioRxiv2019

Transcriptional reprogramming in fused cells is triggered by plasma-membrane diminution

Developing cells divide and differentiate, and in many tissues, such as bone, muscle, and placenta, cells fuse acquiring specialized functions. While it is known that fused-cells are differentiated, it is unclear what mechanisms trigger the programmatic-change, and whether cell-fusion alone drives differentiation. To address this, we employed a fusogen-mediated cell-fusion system involving undifferentiated cells in tissue culture. RNA-seq analysis revealed cell-fusion initiates a dramatic transcriptional change towards differentiation. Dissecting the mechanisms causing this reprogramming, we observed that after cell-fusion plasma-membrane surface area decreases through increased endocytosis. Consequently, glucose-transporters are internalized, and cytoplasmic-glucose and ATP transiently decrease. This low-energetic state activates AMPK, which inhibits YAP1, causing cell-cycle arrest. Impairing either endocytosis or AMPK prevents YAP1 inhibition and cell-cycle arrest after fusion. Together these data suggest that cell-fusion-induced differentiation does not need to rely on extrinsic-cues; rather the plasma-membrane diminishment forced by the geometric-transformations of cell-fusion cause transient cell-starvation that induces differentiation.

cell biology↗

bioRxiv2019

Patchy, incomplete, and heterogeneous X-inactivation in the human placenta

One of the X chromosomes in genetic females is silenced by a process called X chromosome inactivation (XCI). Variation in XCI across the placenta may contribute to observed sex differences and variability in pregnancy outcomes. However, XCI has predominantly been studied in human adult tissues. Here we sequenced and analyzed DNA and RNA from two locations from 30 full-term pregnancies. Implementing an allele specific approach to examine XCI, we report evidence that XCI in the human placenta is patchy, with large patches of either silenced maternal or paternal X chromosomes. Further, using similar measurements, we show that this is in contrast to adult tissues, which generally exhibit mosaic X-inactivation, where bulk samples exhibit both maternal and paternal X chromosome expression. Further, by comparing skewed samples in placenta and adult tissues, we identify genes that are uniquely silenced or expressed in the placenta compared to adult tissues highlighting the need for tissue-specific maps of XCI.

genomics↗