Lymph sacs are not required for the initiation of lymph node formation.
The lymphatic vasculature drains lymph fluid from the tissue spaces of most organs and returns it to the blood vasculature for recirculation. Before reaching the circulatory system, antigens and pathogens transported by the lymph are trapped by the lymph nodes. As proposed by Florence Sabin more than a century ago and recently validated, the mammalian lymphatic vasculature has a venous origin and is derived from primitive lymph sacs scattered along the embryonic body axis. Also as proposed by Sabin, it has been generally accepted that lymph nodes originate from those embryonic primitive lymph sacs. However, we now demonstrate that the initiation of lymph node development does not require lymph sacs. We show that lymph node formation is initiated normally in E14.5 Prox1-null mouse embryos devoid of lymph sacs and lymphatic vasculature, and in E17.5 Prox1 conditional mutant embryos, which have defective lymph sacs. However, subsequent clustering of hematopoietic cells within these developing lymph nodes is less efficient.
Vondenhoff
Mark F
MF
Department of Molecular Cell Biology and Immunology, VU University Medical Center, PO box 7057, 1007 MB Amsterdam, The Netherlands.
van de Pavert
Serge A
SA
Dillard
Miriam E
ME
Greuter
Mascha
M
Goverse
Gera
G
Oliver
Guillermo
G
Mebius
Reina E
RE
D000818:Animals; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D004729:Endothelium, Lymphatic / Q000166:cytology / Q000378:metabolism; D006579:Heterozygote; D018398:Homeodomain Proteins / Q000378:metabolism; D008198:Lymph Nodes / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D042601:Lymphatic Vessels / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D025521:Tumor Suppressor Proteins / Q000172:deficiency / Q000378:metabolism; D000098551:Prospero-Related Homeobox 1 Protein
D018398:Homeodomain Proteins; D025521:Tumor Suppressor Proteins; D000098551:Prospero-Related Homeobox 1 Protein