Identification, visualization and clonal analysis of intestinal stem cells in fish

Area of Science:

• Developmental Biology
• Stem Cell Biology
• Evolutionary Biology

Background:

• Mammalian intestinal stem cells (ISCs) predominantly divide symmetrically, followed by neutral drift.
• Teleost fish retinal stem cells exhibit asymmetric division.
• The evolutionary and developmental pathways of stem cell division modes remain incompletely understood.

Purpose of the Study:

• To investigate the mode of stem cell division in the teleost medaka gastrointestinal tract.
• To determine if stem cell division modes are phylogenetically or ontogenetically determined.
• To explore the functional equivalence of fish ISC niches to mammalian intestinal crypts.

Main Methods:

• X-ray microcomputed tomography to analyze 3D intestinal topography.
• In vitro proliferation assays for ISCs.
• Genetically encoded lineage tracing to track stem cell behavior.
• Gene expression analysis of ISC markers (sox9, axin2, lgr5).

Main Results:

• A distinct ISC niche was identified in the furrows between intestinal folds, analogous to mammalian crypts.
• Medaka ISCs express homologs of key mammalian ISC markers (sox9, axin2, lgr5), indicating Wnt pathway conservation.
• Stochastic labeling revealed that single ISCs contribute to both tissue homeostasis and growth through extended labeled/unlabeled domains.
• Evidence suggests co-evolution of different stem cell division modes within the medaka intestine.

Conclusions:

• Stem cell division modes can co-evolve within a single organism, independent of physical crypt isolation.
• The fish intestinal furrow niche functions analogously to mammalian intestinal crypts.
• Wnt pathway components are evolutionarily conserved in intestinal stem cell niches across vertebrates.