Morphological features of mutant rat, IS‐Tlk/Kyo, fetuses with caudal vertebral anomalies

Abstract

IS-Tlk/Kyo, a rat mutant strain derived from IS/Kyo strain, exhibits a kinked and/or short tail, in addition to a congenital anomaly of the lumbar vertebrae that is a hallmark of IS/Kyo rats. Homozygotes (Tlk/Tlk) of Tlk dominant gene are known to die during embryonic development. The present report deals with the morphological features of heterozygous IS-Tlk/Kyo rat fetuses in comparison with those of IS/Kyo rat fetuses. One of the morphological features was a high incidence of tail vertebral anomalies in IS-Tlk rats (81.6% versus 0% in IS/Kyo rats). Significantly low values in number of live fetuses and ossified 5th sternebra and sacral and caudal vertebrae were observed in IS-Tlk/Kyo rats compared with those in IS/Kyo rats as well as a low incidence of fetuses with ventral septal defects in IS-Tlk/Kyo (0% versus 54.4% in IS rats). These results suggest that the Tlk gene may be involved in the formation of the vertebral centra and the ventral septum when it expresses on the genetic background of the IS rat.

Morphological Features of Adult Rats of IS/Kyoand IS-<i>Tlk</i>/Kyo Strains with Lumbar and Caudal Vertebral Anomalies

“…of fetuses with VSD/Total No. of fetuses examined: 21/35, [ 19 ]), indicating reduction in the incidence and size of VSD during postnatal development. It was reported that mild VSD induced by the critical exposure of fetuses to teratogens tended to disappear during neonatal development due to natural closure of VSD [ 18 ] and that fetuses with severe VSD died after birth [ 6 ].…”

“…The carcasses of female rats of IS strain were subjected to alizarin red S staining to prepare skeletal specimens. Skeletal specimens of adult rats of IS/T strain were obtained from the previous study [ 19 ]. The length of total sacral and caudal vertebrae was measured in rat fetal skeletons prepared in the previous study [ 19 ] by a Digital Microscope (VHX-2000, KEYENCE CORPORATION) and in adult rat skeleton by a vernier micrometer.…”

“…Previously, we investigated the morphological features of IS/T rat fetuses in comparison with those of IS rat fetuses [ 19 ], and the outline of the morphological features obtained was as follows: 1) a high incidence of tail vertebral anomalies in IS/T rats (81.6% versus 0% in IS rats), 2) retarded ossification of 5th sternebra and sacral and caudal vertebrae in IS/T rats (incidence in 5th sternebra: 23.8% versus 70.5% in IS rats, mean values in sacral and caudal vertebrae: 5.81 versus 6.24 in IS rats) and 3) a low incidence of fetuses with ventral septal defects in IS/T rats (0% versus 54.4% in IS rats). From these results, we suggested that Tlk gene might be involved in the formation of the vertebral centra and the ventral septum when it expresses on the genetic background of the IS rats.…”

“…This study was performed to clarify the morphological changes in adult IS and IS/T mutant rats and to consider how well these rats may serve as models of human congenital pathology. In addition, to reveal a characteristic of short tail in IS/T rats, we examined the difference in the length of sacral and caudal vertebrae between two strains using skeletal specimens obtained from the previous study [ 19 ] and adult rats.…”

“…Homozygotes of Tlk dominant gene are known to die during embryonic development. We previously reported the morphological features of the skeleton in IS / Kyo and IS- Tlk/ Kyo fetuses and of the heart in IS/Kyo fetuses [ 19 ]. This study was conducted to clarify the morphological features of the skeleton in both adult rats and of the heart in adult IS/Kyo rats.…”