title: Immunotargeting and cloning of two CD34 variants exhibiting restricted expression in adult rat endothelia in vivo.
abstract: Mapping protein expression of endothelial cells (EC) in vivo is fundamental to understanding cellular function and may yield new tissue-selective targets. We have developed a monoclonal antibody, MAb J120, to a protein expressed primarily in rat lung and heart endothelium. The antigen was identified as CD34, a marker of hematopoietic stem cells and global marker of endothelial cells in human and mouse tissues. PCR-based cloning identified two CD34 variant proteins, full length and truncated, both of which are expressed on luminal endothelial cell plasma membranes (P) isolated from lung. Truncated CD34 predominated in heart P, and neither variant was detected in P from kidney or liver. CD34 in lung was readily accessible to (125)I-J120 inoculated intravenously, and immunohistochemistry showed strong CD34 expression in lung EC. Few microvessels stained in heart and kidney, and no CD34 was detected in vessels of other organs or in lymphatics. We present herein the first complete sequence of a rat CD34 variant and show for the first time that the encoded truncated variant is endogenously expressed on EC in vivo. We also demonstrate that CD34 expression in rat EC, unlike mouse and human, is restricted in its distribution enabling quite specific lung targeting in vivo.
authors.affiliation: Proteogenomics Research Institute For Systems Medicine, Sidney Kimmel Cancer Center, San Diego, CA 92121, USA. jtesta@prism-sd.org
authors.forename: Jacqueline E
authors.initials: JE
authors.lastname: Testa
authors.forename: Adrian
authors.initials: A
authors.lastname: Chrastina
authors.forename: Phil
authors.initials: P
authors.lastname: Oh
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Halina
authors.initials: H
authors.lastname: Witkiewicz
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Czarny
authors.forename: Tim
authors.initials: T
authors.lastname: Buss
authors.forename: Jan E
authors.initials: JE
authors.lastname: Schnitzer
mesh_terms: D000367:Age Factors; D017398:Alternative Splicing / Q000276:immunology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D018952:Antigens, CD34 / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D001011:Aorta / Q000166:cytology; D002478:Cells, Cultured; D003001:Cloning, Molecular; D042783:Endothelial Cells / Q000166:cytology / Q000502:physiology*; D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D008168:Lung / Q000166:cytology / Q000000981:diagnostic imaging / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009928:Organ Specificity; D016133:Polymerase Chain Reaction; D051381:Rats; D011916:Rats, Inbred F344; D013045:Species Specificity; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D000911:Antibodies, Monoclonal; D018952:Antigens, CD34