In the mammalian intestine, stem cells (ISCs) located in basal crypts, replicate and translocate along the villus where they die and are shed from the tips. This conveyer belt-like pattern of absorptive surface renewal is generally thought to occur in the less advanced architecture of the zebrafish intestine in which villi are elongated into villar ridges (VR) and crypts are absent. To understand how epithelial dynamics is maintained without crypts, we imaged the lineage patterns of epithelia driven by promoters for ISC markers, Prmt1, Lrig1, and Bmi1. All three markers generate distinct stripes of Zebrabow recombinant colors that originate from the intervillus pocket (IVP) between neighboring villa ridges. The striping pattern is not only consistent with ISCs in an IVP but also a non-random ISC distribution in the IVP. We confirmed that the ISC marker, Prmt1, is localized to a single cell within a 40-60 µm diameter flat cluster of cells at the base of the intervillus pocket. Furthermore, the color and width of recombinant epithelial stripes on the flanking VRs share the same recombinant color and dimension as these clusters. These results identify Prmt1, Bmi1, and Lrg1 as ISC markers and that the ISCs reside within basal clusters that are functionally analogous to a crypt. We propose that the villus/crypt architecture of our intestine evolved from further differentiation of these flat crypt-like structure into the elongated crypt. This structure has implications for future tissue engineering strategies.
For this graduate thesis Paul Matsudaira studied the intestine villus cytoskeleton and was awarded his PhD in Biological Sciences from Dartmouth College in 1981 then carried out postdoctoral research on the dynamics and assembly of the intestine villus cytoskeleton at the Max Planck for Biophysical Chemistry (Goettingen, Germany) and the MRC Laboratory for Molecular Biology (Cambridge, UK). In 1985, he joined the Whitehead Institute, MIT Department of Biology, and later was on the founding faculty of the MIT Department of Biological Engineering rising to the rank of Professor of Biology and Professor of Bioengineering. His lab studied the structure and biomechanics of cells and tissues and developed microanalytical methods. At MIT he served as Associate Chair of the MIT Faculty, Director of the WI-MIT BioImaging Center, Director of the Computational and Systems Biology Initiative (CSBi) and was on the author team of the Lodish textbook, Molecular Cell Biology. In 2009, he moved to the National University of Singapore as Head of the Department of Biological Sciences, Founding Director of the NUS Centre for BioImaging Sciences, and Founding co-Director of the MechanoBiology Institute. In 2019, he was awarded the rank of Professor Emeritus and continues research into the mechanobiology of early zebrafish development.
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