We use human pluripotent stem cells (PSCs) to model embryo development in vitro and understand the mechanisms that regulate cell fate decisions during human neuromuscular system development. During embryonic development spinal cord motor neurons are generated with high precision along the anterior-posterior (AP) axis and establish connections with skeletal muscles to control movement. Previous studies have shown that development and survival of motor neurons and muscles depend on each other but until recently their generation were considered as independent events. Striking evidence coming from clonal lineage analysis experiments in the mouse embryo suggested that a common bipotent progenitor exists in vivo that can give descendants to both the spinal cord and paraxial mesoderm (Tzouanacou et al, 2009). These cells, called neuromesodermal progenitors (NMPs), reside in the caudal lateral epiblast region of the embryo and are important for axis elongation and correct tissue growth but have been largely ignored in the stem cell field.
Following the cues from embryonic development, we have succeeded in generating NMP cells in vitro from mouse and human pluripotent stem cells (Gouti et al, 2014; Gouti et al, 2017). The in vitro generation of these cells opens up new opportunities for the study and treatment of neuromuscular diseases as it gives unprecedented access to the simultaneous development of both neural and mesodermal cell types in the “dish”. Our focus is to understand how these two tissues are generated and interact in space and time during human development and disease. This will allow us to unravel the mechanisms of human embryo development and evaluate how defects in the early development of these tissues may predispose to disease in adult life.
Recently, we used the in vitro derived NMPs to generate human 3D neuromuscular organoids (NMOs) that self-organise into distinct spinal cord neural and skeletal muscle compartments. NMOs contain functional neuromuscular junctions supported by terminal Schwann cells, they contract and develop central pattern generator-like neuronal circuits. NMOs can be maintained as 3D structures for several months, while the component tissues mature, giving unprecedented access to human developmental events and allowing analysis of the specific contributions of different cell types to neuromuscular disorders (Faustino Martins et al, Cell Stem Cell, 2020). We have successfully used NMOs to recapitulate key aspects of myasthenia gravis (MG) pathology. We are currently using the neuromuscular 2D and 3D models established in our lab to study spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS) and muscular dystrophies (MD).
To address the mechanisms of development and disease we are using gain and loss of gene function approaches (crispr/cas9), next-generation sequencing technologies (single cell RNA-seq) as well as live cell imaging techniques.