Identification of the modifier locus that suppresses neonatal lethality in (female symbolDDD x male symbolDH- Dh/+) F(1)-Dh/+ male mice.
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Most F(1)-Dh/+ male mice resulting from a cross between inbred DDD strain females and DH-Dh/+ strain males exhibit growth retardation and die during the neonatal period. The lethality is caused by a combination of three independent gene loci, namely the Dh locus on chromosome 1, Grdhq1 locus on the X chromosome, and a putative Y chromosome-linked locus in some strains. Among these loci, Grdhq1 was previously mapped to a distal region of the X chromosome using progeny fromfemale symbol(female symbolDDD x male symbolDH-+/+) F(1) x male symbolDH-Dh/+ mice. In this study, fine mapping of Grdhq1 was performed using progeny of female symbol(female symbolDDD x male symbolCAST/EiJ) F(1) male symbolDH-Dh/+ mice. Contrary to expectation, Dh/+ male pups carrying the DDD allele at DXMit135 (genetic marker nearest to Grdhq1) survived to weaning. The presence of modifier loci that suppressed the lethality by impeding the action of Grdhq1 was suggested; therefore, a genome-wide scan was performed in the surviving Dh/+ males. As a result, a significant modifier locus was identified on proximal chromosome 11. This in turn suggested that Grdhq1 was located more distally than we had expected; that is, the actual location of Grdhq1 appeared to be near and/or distal to the Mid1 locus. Thus, the results revealed that the neonatal lethality in (DDD x DH-Dh/+) F(1)-Dh/+ males was caused by the fourth gene locus on chromosome 11 in addition to the above-mentioned three gene loci on chromosomes 1, X, and Y. (+info)
Prenatal diagnosis of sirenomelia in the late second trimester with three-dimensional helical computed tomography.
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Sirenomelia is a rare congenital syndrome that is characterized by the anomalous development of the caudal region of the body. The anomalies include bilateral renal agenesis or dysgenesis and the absence of the sacrum and other vertebral defects. Sirenomelia is also known as "mermaid syndrome," because of the one lower extremity. It is usually associated with severe oligohydramnios, and its prognosis is very poor due to pulmonary hypoplasia that is caused by severe oligohydramnios. The patient referred to our hospital at the gestational age of 27 weeks with fetal growth restriction and oligohydramnios. The estimated fetal body weight was 970 g (-4.9 S.D.). We could identify only one-side extremities, and could not identify kidneys by ultrasound examination. Because a single lower extremity and severe oligohydramnios are characteristics of the sirenomelia, we suspected sirenomelia. However, it could not be confirmed by ultrasound examination because of oligohydramnios. Therefore, we performed three-dimensional helical computed tomography (3D-CT), which is more accurate than ultrasound examinations for prenatal diagnosis of skeletal abnormalities. 3D-CT revealed an only one lower extremity. At 36 weeks and 5 days of gestation, the woman went into spontaneous labor and delivered an infant weighing 870 g. The infant has a single upper extremity and a single lower extremity. We provided supportive care for the neonate, who however died 1 hour 36 minutes after birth from severe respiratory distress. In summary, we report the correct diagnosis of sirenomelia with 3D-CT in the late second trimester. (+info)
Residual malformations and leg length discrepancy after treatment of fibular hemimelia.
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