Kenichiro (Ken) Taniguchi, PhD
Postdoctoral Fellowship, University of Michigan Medical School
PhD, Cell Biology, University of Virginia School of Medicine
BS, Genetics, Cell Biology and Development, University of Minnesota
Stem cell-based tools to investigate molecular and cellular mechanisms of early human embryogenesis
About us – Early human developmental biology
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 human pluripotent stem cell (hPSC)-based in vitro organoid models (Taniguchi et al., Stem Cell Reports 2015, Shao, Taniguchi et al., Nature Materials 2017, Shao, Taniguchi et al., Nature Communications 2017, Taniguchi, Shao et al., Journal of Cell Biology 2017, reviewed in Taniguchi et al., Journal of Cell Biology 2019) in conjunction with single-cell, proteomic and genome editing tools.
Implantation of the human embryo into the uterine wall represents a critical developmental milestone; up to 50% of pregnancies fail during this important peri-implantation period. However, 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. To circumvent these limitations, we employ stem cell-based platforms that allow us to mechanistically probe human peri-implantation embryogenic events, in particular pro-amniotic cavity formation and amniogenesis (some examples shown in Fig. 1).
In humans, the pro-amniotic cavity (amniotic fluid reservoir) is formed immediately after implantation. Its formation is initiated from a cluster of pluripotent stem cells (called the inner cell mass) that undergo apico-basal polarization to form a spheroid structure with a central lumenal cavity (Fig. 2). Research from my laboratory show that lumen formation is driven by a novel intracellular structure called the apicosome (Taniguchi, Shao et al., JCB 2017). Shortly after lumenogenesis, one pole (facing uterus) of this initially uniform lumenal cyst of pluripotent cells differentiates into squamous amniotic ectoderm, and a sharp boundary forms between amnion and epiblast (embryonic) portions of the spheroid. This structure – termed the amniotic sac – represents the substrate for the next essential steps of embryonic development including primitive streak formation and gastrulation (Fig. 2, E14-15). hPSC (e.g., hESC – human embryonic stem cells, hiPSC – human induced pluripotent stem cells) have been validated as an excellent system to model these peri-implantation events.
Major goals of the Taniguchi lab are to advance the understanding of how:
- The apicosome drives the formation of the pro-amniotic cavity
- Amnion fate is determined
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 (the pro-amniotic cavity, Fig. 2). Recently, epiblast polarization and lumen formation have been investigated using hPSC. In singly dissociated hPSC, a lumen forms along the cytokinetic plane following the first cell division (2-cell cyst), and these cysts quickly grow into multi-cellular lumenal spheroids in which all cells retain pluripotency (hPSC-spheroid, Fig. 1, Taniguchi et al., Stem Cell Reports 2015). When dissociated hPSC are plated densely to allow the formation of aggregates, seemingly unpolarized collections of hPSC initiate radial organization and form a lumenal spheroid (Fig. 3 and Movie 1) in a manner similar to epiblast cavity formation in vivo (Fig. 2). 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 (Fig. 4 and Movie 2, Taniguchi, Shao et al., JCB 2017). Our data show that the apicosome functions as a pre-made lumenal precursor that fast-tracks lumen formation during pro-amniotic cavity development.
Movie 1: Time-lapse imaging of hPSC-spheroid formation driven by the apicosome.
Movie 2: Dynamics of apicosomal microvilli labeled by EZRIN-GFP
We currently have two major objectives in our apicosome research:
- Identify building blocks of the apicosome at a global proteomic level
- Elucidate molecular machineries and signaling events controlling apicosome formation and trafficking.
We combine cutting-edge genetic (e.g., transgenic, genome editing), proteomic and imaging tools to dissect mechanisms regulating apicosome biogenesis in hPSC. Students and postdocs will have a unique opportunity to engage in efforts to screen for proteins that regulate apicosome formation, and to undertake new and exciting projects that examine 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 cavity (Fig. 2). Initially, the pro-amniotic cavity is surrounded by epiblast cells and shows symmetrical morphology. As implantation proceeds, epiblast cells that are proximal to the uterus (at this stage being invaded by cytotrophoblast cells) begin to flatten as they take on amnion fate, while cells on the opposite side of the cyst, adjacent to the primitive endoderm (facing toward the yolk sac cavity), become more columnar, forming the embryonic disc (precursor to the embryo proper). 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). However, 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-spheroid toward amnion lineage. In these conditions, hPSC-spheroids undergo progressive cellular flattening, loose pluripotency, and acquire morphological (squamous) and transcriptomic features consistent with amniotic (Movie 3, 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 (Fig. 5). Using state-of-the-art tools such as genome editing and high-throughput RNA sequencing, we are actively investigating:
- How the mechanical cue results in the activation of BMP signaling
- What are the BMP-responsive transcription factors that enable the differentiation toward amniotic lineage from pluripotent cell types (pioneer factor)
Movie 3: hPSC-spheroid forming squamous hPSC-amnion
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.
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.
(Taniguchi K, Heemskerk I, Gumucio DL.) J Cell Biol. 2019 02 04;218(2):410-421.
(Wotton D, Taniguchi K.) Am J Med Genet C Semin Med Genet. 2018 06;178(2):128-139.
(Taniguchi K, Shao Y, Townshend RF, Cortez CL, Harris CE, Meshinchi S, Kalantry S, Fu J, O'Shea KS, Gumucio DL.) J Cell Biol. 2017 12 04;216(12):3981-3990.
(Shao Y, Taniguchi K, Townshend RF, Miki T, Gumucio DL, Fu J.) Nat Commun. 2017 08 08;8(1):208.
(Shao Y, Taniguchi K, Gurdziel K, Townshend RF, Xue X, Yong KMA, Sang J, Spence JR, Gumucio DL, Fu J.) Nat Mater. 2017 04;16(4):419-425.
(Anderson AE, Taniguchi K, Hao Y, Melhuish TA, Shah A, Turner SD, Sutherland AE, Wotton D.) Mol Cell Biol. 2017 03 01;37(5).
(Taniguchi K, Anderson AE, Melhuish TA, Carlton AL, Manukyan A, Sutherland AE, Wotton D.) Eur J Hum Genet. 2017 02;25(2):208-215.
(Freddo AM, Shoffner SK, Shao Y, Taniguchi K, Grosse AS, Guysinger MN, Wang S, Rudraraju S, Margolis B, Garikipati K, Schnell S, Gumucio DL.) Integr Biol (Camb). 2016 09 12;8(9):918-28.
(Melhuish TA, Taniguchi K, Wotton D.) PLoS One. 2016;11(5):e0155837.
(Taniguchi K, Shao Y, Townshend RF, Tsai YH, DeLong CJ, Lopez SA, Gayen S, Freddo AM, Chue DJ, Thomas DJ, Spence JR, Margolis B, Kalantry S, Fu J, O'Shea KS, Gumucio DL.) Stem Cell Reports. 2015 Dec 08;5(6):954-962.
(Taniguchi K, Anderson AE, Sutherland AE, Wotton D.) PLoS Genet. 2012;8(2):e1002524.
(Powers SE, Taniguchi K, Yen W, Melhuish TA, Shen J, Walsh CA, Sutherland AE, Wotton D.) Development. 2010 Jan;137(2):249-59.