Stem cell-based tools to investigate molecular and cellular mechanisms of early human embryogenesis

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News

November 2021

Nikola was selected to receive the MCW Postdoc Professional Developmental Award! Congrats!

August 2021

We welcome Anusha Rengarajan, a new graduate student who will be working on mechanisms underlying apicosome formation!

May 14, 2021

Amber Carleton was the 1st place graduate student winner in the MCW Scientific Image Contest – great job, Amber!

Description: This 5 week old cerebral brain organoid displays three neural rosettes with open lumenal regions. Immunofluorescence shows nuclear stain (blue), early-born neuron stain (green) and F-actin (white). Photo taken on Zeiss Confocal Microscope.

April 23, 2021

Our recent publication made great strides in understanding mechanisms governing human epiblast formation (Wang et al., Science Advances 2021). We employed APEX2-based spatial biotinylation, followed by quantitative mass spectrometry, to systematically profile apical and basolateral proteomes (cell polarity proteome) in live human pluripotent stem cell (hPSC)-derived 3D human epiblast-like cysts (hPSC-cysts), and uncovered key molecules required for polarization and the critical trafficking machinery involved in apicosome formation and lumenogenesis.

About us - Early human developmental biology

Implantation of the human embryo into the uterine wall represents a critical developmental milestone; up to 50% of pregnancies/fetal development fail during this important peri-implantation period. The exact causes of early implantation failure remain largely unknown given the technical and ethical limitations of studying this developmental time period in the human.

Our goal is to understand molecular and cellular mechanisms of peri-implantation human development, a period referred to as the “black box” of human embryogenesis, using animal as well as hPSC-based in vitro organoid models that enable us to mechanistically probe human peri-implantation embryogenic events, in particular the formation of the epiblast structure and the pro-amniotic cavity (amniotic fluid reservoir), as well as amniogenesis (e.g., hPSC-cyst and hPSC-amnion shown in the figure). Our recent work (hPSC-cyst – Taniguchi et al., Stem Cell Reports 2015, hPSC-amnion – Shao, Taniguchi et al., Nature Materials 2017, PASE – Shao, Taniguchi et al., Nature Communications 2017, apicosome – Taniguchi, Shao et al., Journal of Cell Biology 2017, reviewed in Taniguchi et al., Journal of Cell Biology 2019) established that hPSC (e.g., hESC – human embryonic stem cells, hiPSC – human induced pluripotent stem cells) are an excellent system to model processes that occur during human peri-implantation, and offered two important discoveries: 1) apicosome, a novel organelle, promotes epiblast lumen formation, and 2) amniogenesis is triggered in the pluripotent epiblast cells facing the uterine wall by a mechanically activated BMP signaling, forming the amniotic sac-like structure.

Major goals of the Taniguchi lab are to advance the understanding of how:

1. The apicosome drives the formation of the epiblast and the pro-amniotic cavity
2. Amnion fate is determined

Importantly, our research will advance fundamental understanding of epithelial morphogenesis, mechanosensitive signaling as well as mechanically activated BMP signaling, and, clinically, we expect that these explorations will result in new diagnostic and therapeutic strategies for infertility.

Focus 1 – Cell biology of the apicosome

Upon implantation, the aggregate of epiblast cells undergoes a dramatic reorganization: cells polarize along their apico-basal axis and adopt a rosette-like structure with a central shared lumen (epiblast/pro-amniotic cavity). Recently, epiblast cell polarization and epiblast/pro-amniotic cavity formation have been investigated using hPSC-cyst (Taniguchi et al., Stem Cell Reports 2015), and, we found that the steps of hPSC-cyst formation are similar to epiblast lumen formation in vivo, in which seemingly unpolarized collections of hPSC initiate radial organization then a central lumen formation. Mechanistically, this process is driven by an apicosome – an apically charged organelle with characteristics of an intracellular lumen, complete with microvilli, primary cilium and increased concentration of calcium (Taniguchi, Shao et al., Journal of Cell Biology 2017). Our data show that the apicosome functions as a pre-made lumenal precursor that fast-tracks lumen formation during pro-amniotic cavity development, and we recently demonstrated a novel requirement of the AP-1 clathrin adaptor complex in apicosome formation (Wang et al., Science Advances 2021).

We currently have two major objectives in our apicosome research:

1. Identify building blocks of the apicosome and polarized epithelium at global proteomic levels
2. Elucidate molecular machineries and signaling events controlling apicosome formation and trafficking.

Students and postdocs will have a unique opportunity to engage in efforts to screen for proteins that regulate apicosome formation and lumenogenesis, and to undertake new and exciting projects examining fundamental aspects of apicosome biology.

Focus 2 – Amnion development

Amnion is a vital component of fetal development. Amnion is an amniotic fluid reservoir, and functions to provide physical protection to the fetus, as well as to aid in development (nutrients, hormones, etc.). During human development, amnion forms around 7-8 dpc (days post coitum) immediately following the formation of the pro-amniotic/epiblast cavity. Due to ethical and technical concerns, the study of human embryos at this early stage of development is prohibited; because of this lack of suitable human in vitro models for mechanistic studies, these initial stages of amniogenesis are not well understood in the human.

To study these early events, we developed culture conditions that allow directed differentiation of hPSC-cyst toward amnion lineage. In these conditions, hPSC-cysts undergo progressive cellular flattening, loose pluripotency, and acquire morphological (squamous) and transcriptomic features consistent with amniotic (hPSC-amnion, Shao, Taniguchi et al., Nature Materials 2017). The hPSC-amnion model enables mechanistic analyses of amnion development, and we have already discovered that the activation of the bone morphogenetic protein (BMP) signaling pathway (downstream of mechanical cue in the 3D culture condition) is critical for the initial step of amnion specification by activating an amniotic transcriptional cascade. Using state-of-the-art tools such as genome editing and high-throughput RNA sequencing, we are actively investigating:

1. How the mechanical cue results in the activation of BMP signaling
2. What are the BMP-responsive transcription factors that enable the differentiation toward amniotic lineage from pluripotent cell types (pioneer factor)

Clinically, there are several notable amnion-related conditions that endanger both fetus and mother, such as pre-term premature rupture of fetal membranes (pPROM, premature amnion rupture due to premature weakening of the fetal membrane) and constriction band syndrome (CBS, amputation of fetal extremities as a torn amnion constricts part of the fetus). Exploration of mechanisms regulating amniogenesis will expand our understanding of these pathological conditions.

This is an exciting opportunity for graduate students and postdocs to participate in the discovery of novel amniotic transcription factors, uncover additional mechanisms of amniogenesis, and embark on generating further refined platforms that enable studies of amniogenesis at various developmental stages.

Recruiting!

The Taniguchi lab is actively recruiting highly motivated graduate students and post-doctoral scientists from broad areas (not limited to stem cell or developmental biology, e.g., biophysics, biochemistry, cell biology, bioinformatics, engineering) with new ideas and interests in stem cell and human developmental biology.

Postdoctoral Scientists - Open Position Details