Em. Garabedian et al., EXAMINING THE ROLE OF PANETH CELLS IN THE SMALL-INTESTINE BY LINEAGE ABLATION IN TRANSGENIC MICE, The Journal of biological chemistry, 272(38), 1997, pp. 23729-23740
The Paneth cell lineage is one of four epithelial lineages derived fro
m the adult mouse small intestine's multipotent stem cell, Mature Pane
th cells secrete antimicrobial peptides (cryptdins), growth factors, a
s well as two gene products, a secreted phospholipase A, and matrilysi
n, that has been implicated as modifiers of adenoma formation in mice
containing a mutation in the tumor suppressor Apc. Immature Paneth cel
ls are located just above and below the cell layer, in intestinal cryp
ts, that has been proposed to contain the multipotent stem cell. Panet
h cells differentiate during a downward migration to the crypt base. T
he location and direction of Paneth cell migration, their high density
and long residency time at the crypt base, and the nature of their se
creted gene products, suggest that they may influence the structure an
d/or function of the stem cell niche. Paneth cell ablation can therefo
re be viewed as an experimental manipulation of the cellular microenvi
ronment that purportedly contains the stem cell and its immediate desc
endants, Two types of ablation experiments were performed in transgeni
c mice. Nucleotides -6500 to +34 of the mouse cryptdin-2 gene (CR2) we
re used to express an attenuated diphtheria toxin A fragment, Light an
d electron microscopic immunohistochemical analyses of several pedigre
es of postnatal day 28 to 180 animals established that ablation of Pan
eth cells is accompanied by an increase in the proportion of undiffere
ntiated crypt base columnar cells, These cells normally co-exist with
Paneth cells, The ablation does not produce a detectable effect on the
proliferation or terminal differentiation programs of the other three
lineages or on host-microbial interactions, Tile last conclusion is b
ased on the ability of crypts to remain free of microbes detectable by
Gram and Warthin-Starry stains and by retention of the normal crypt-v
illus distribution of components of the diffuse gut-associated lymphoi
d tissue, CR2-directed expression of simian virus 40 large T antigen a
lso results in a loss of mature Paneth cells but produces a marked amp
lification of crypt cells having a morphology intermediate between Pan
eth and granule goblet cells, EM immunohistochemical analyses suggest
that intermediate cells can differentiate to mature goblet cells but n
ot to Paneth cells, as they migrate up the crypt-villus axis, Our find
ings suggest that (i) stemness in the crypt is not defined by instruct
ive interactions involving the Paneth cell; (ii) expressing a Paneth c
ell fate may require that precursors migrate to the crypt base; (iii)
antimicrobial factors produced by Paneth cells are not required to pre
vent colonization of small intestinal crypts; and (iv) this lineage do
es not function to maintain the asymmetric crypt-villus distribution o
f components of the diffuse gut-associated lymphoid tissue.