Temporal and spatial expression of caudal-type homeobox gene-1 in the development of anorectal malformations in rat embryos.
OBJECTIVE
The aim of this study was to determine caudal-type homeobox gene-1 (Cdx1) expressions during anorectal development in normal and anorectal malformation (ARMs) embryos and investigate the possible role of Cdx1 in the pathogenesis of ARM.


METHODS
Anorectal malformation was induced by ethylenethiourea on the 10th gestational day (GD10) in rat embryos. Cesarean deliveries were performed to harvest embryos from GD13 to GD21. The temporal and spatial expression of Cdx1 was evaluated in normal rat embryos (n = 334) and ARM embryos (n = 328) from GD13 to GD20 using immunohistochemistry staining, reverse transcriptase polymerase chain reaction (RT-PCR), and Western blot analysis.


RESULTS
Immunostaining revealed that in normal embryos, on GD13.5, Cdx1 expression was mainly located on the epithelium of the dorsal urorectal septum (URS), cloacal membrane, and the hindgut. On GD15, increased positive tissue staining was noted on the fused tissue of URS, especially in the very thin anal membrane. In the ARM embryos, however, the epithelium of the cloaca, URS, and anorectum was negative or faint for Cdx1. In Western blot and RT-PCR, in the normal group, Cdx1 protein and Cdx1 messenger RNA expression showed time-dependent changes in the developing hindgut, on GD14, GD14.5, and GD15. The expression level reached a peak when the anus was forming. Once the anus was open, Cdx1 expression gradually decreased. In addition, the expression level of Cdx1 in the ARM group from GD13 to GD16 was significant lower than that of the normal group (P < .05).


CONCLUSIONS
In ARM embryos, an imbalance of spatiotemporal expression of Cdx1 was noted during anorectal morphogenesis from GD13 to GD16. This suggests that downregulation of Cdx1 at the time of cloacal separation into rectum and urethra might be related to the development of ARM.
Zhang
Tao
T
Department of Pediatric Surgery, Shengjing Hospital, China Medical University, Shenyang 110004, PR China.
Bai
Yu Zuo
YZ
Zhang
Dan
D
Zhang
Shi Wei
SW
Wang
Da Jia
da J
Jia
Hui Min
HM
Yuan
Zheng Wei
ZW
Wang
Wei Lin
WL
D001003:Anal Canal / Q000002:abnormalities* / Q000196:embryology / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D004065:Digestive System Abnormalities / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D005031:Ethylenethiourea; D018398:Homeodomain Proteins / Q000235:genetics*; D007124:Immunoenzyme Techniques; D051381:Rats; D012007:Rectum / Q000002:abnormalities* / Q000196:embryology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D018398:Homeodomain Proteins; D005031:Ethylenethiourea