Standardizing designed and emergent quantitative features in microphysiological systems.

Microphysiological systems (MPSs) are cellular models that replicate aspects of organ and tissue functions in vitro. In contrast with conventional cell cultures, MPSs often provide physiological mechanical cues to cells, include fluid flow and can be interlinked (hence, they are often referred to as microfluidic tissue chips or organs-on-chips). Here, by means of examples of MPSs of the vascular system, intestine, brain and heart, we advocate for the development of standards that allow for comparisons of quantitative physiological features in MPSs and humans.

Chromatin targeting of the RNF12/RLIM E3 ubiquitin ligase controls transcriptional responses.

Protein ubiquitylation regulates key biological processes including transcription. This is exemplified by the E3 ubiquitin ligase RNF12/RLIM, which controls developmental gene expression by ubiquitylating the REX1 transcription factor and is mutated in an X-linked intellectual disability disorder. However, the precise mechanisms by which ubiquitylation drives specific transcriptional responses are not known.

SPEN is required for Xist upregulation during initiation of X chromosome inactivation.

At initiation of X chromosome inactivation (XCI), Xist is monoallelically upregulated from the future inactive X (Xi) chromosome, overcoming repression by its antisense transcript Tsix. Xist recruits various chromatin remodelers, amongst them SPEN, which are involved in silencing of X-linked genes in cis and establishment of the Xi. Here, we show that SPEN plays an important role in initiation of XCI.

REX1 is the critical target of RNF12 in imprinted X chromosome inactivation in mice.

In mice, imprinted X chromosome inactivation (iXCI) of the paternal X in the pre-implantation embryo and extraembryonic tissues is followed by X reactivation in the inner cell mass (ICM) of the blastocyst to facilitate initiation of random XCI (rXCI) in all embryonic tissues. RNF12 is an E3 ubiquitin ligase that plays a key role in XCI. RNF12 targets pluripotency protein REX1 for degradation to initiate rXCI in embryonic stem cells (ESCs) and loss of the maternal copy of Rnf12 leads to embryonic lethality due to iXCI failure.

Pathogenic variants in E3 ubiquitin ligase RLIM/RNF12 lead to a syndromic X-linked intellectual disability and behavior disorder.

RLIM, also known as RNF12, is an X-linked E3 ubiquitin ligase acting as a negative regulator of LIM-domain containing transcription factors and participates in X-chromosome inactivation (XCI) in mice. We report the genetic and clinical findings of 84 individuals from nine unrelated families, eight of whom who have pathogenic variants in RLIM (RING finger LIM domain-interacting protein). A total of 40 affected males have X-linked intellectual disability (XLID) and variable behavioral anomalies with or without congenital malformations.

Sox2 regulates the emergence of lung basal cells by directly activating the transcription of Trp63.

Lung development is determined by the coordinated expression of several key genes. Previously, we and others have shown the importance of the sex determining region Y-box 2 (Sox2) gene in lung development. Transgenic expression of Sox2 during lung development resulted in cystic airways, and here we show that modulating the timing of ectopic Sox2 expression in the branching regions of the developing lung results in variable cystic lesions resembling the spectrum of the human congenital disorder congenital cystic adenomatoid malformation (CCAM).

RNF12 initiates X-chromosome inactivation by targeting REX1 for degradation.

Evolution of the mammalian sex chromosomes has resulted in a heterologous X and Y pair, where the Y chromosome has lost most of its genes. Hence, there is a need for X-linked gene dosage compensation between XY males and XX females. In placental mammals, this is achieved by random inactivation of one X chromosome in all female somatic cells.

Sox2 cooperates with Chd7 to regulate genes that are mutated in human syndromes.

The HMG-box transcription factor Sox2 plays a role throughout neurogenesis and also acts at other stages of development, as illustrated by the multiple organs affected in the anophthalmia syndrome caused by SOX2 mutations. Here we combined proteomic and genomic approaches to characterize gene regulation by Sox2 in neural stem cells. Chd7, a chromatin remodeling ATPase associated with CHARGE syndrome, was identified as a Sox2 transcriptional cofactor.

Long Noncoding RNAs and X Chromosome Inactivation.

In female somatic cells, one of the two X chromosomes is inactivated to equalize the dose of sex-linked gene products between female and male cells. X chromosome inactivation X chromosome inactivation (XCI) is initiated very early during development and requires Xist Xist , which is a noncoding X-linked gene. Upon initiation of XCI, Xist-RNA spreads along the X chromosome in cis, and Xist spreading is required for the recruitment of different chromatin remodeling complexes involved in the establishment and maintenance of the inactive X chromosome.

Exportin 4 mediates a novel nuclear import pathway for Sox family transcription factors.

SRY and other Sox-type transcription factors are important developmental regulators with various implications in human disease. In this study, we identified Exp4 (exportin 4) as an interaction partner of Sox2 in mouse embryonic stem cells and neural progenitors. We show that, besides its established function in nuclear export, Exp4 acts as a bona fide nuclear import receptor for Sox2 and SRY.

Sox2 is important for two crucial processes in lung development: branching morphogenesis and epithelial cell differentiation.

The primary lung bud originates from the foregut and develops into the bronchial tree by repetitive branching and outgrowing of the airway. The Sry related HMG box protein Sox2 is expressed in a cyclic manner during initiation and branching morphogenesis of the lung. It is highly expressed in non-branching regions and absent from branching regions, suggesting that downregulation of Sox2 is mandatory for airway epithelium to respond to branch inducing signals.