The closely related homeobox genes prx-1 and prx-2 are expressed in lateral plate and limb bud mesoderm, but targeted inactivation of these genes failed to demonstrate a limb phenotype. Here we report that mice carrying compound mutations in prx-1 and prx-2 have severe limb deformities. In the forelimb autopod, pre- and postaxial polydactyly were found most commonly, but also syndactyly, oligodactyly, and abnormal digit placement affecting posterior elements were observed. In the hindlimb, preaxial polydactyly with variable expressivity was seen in all cases. Extreme distal digit duplications were seen in both the fore- and hindlimbs. prx-1; prx-2 double-mutant mice also displayed extreme shortening and impaired ossification of the hindlimb zeugopods. Integrity of the forelimb apical ectodermal ridge was abnormal as determined by expression of FGF8 and BMP4. Expression of msx-1 and msx-2, markers for BMP signaling pathways, was absent in regions of the posterior handplates, while expression of Shh and patched was unaffected. The mutant phenotypes were dosage dependent, since prx-1 -/-; prx-2 +/- mice also displayed severe limb abnormalities. These data suggest that prx-1 and prx-2 cooperatively regulate handplate and hindlimb zeugopod morphogenesis through BMP-mediated signaling pathways.
ABSTRACT. Rickets and osteopenia, common problems in chronic childhood cholestasis, have been attributed to vitamin D malabsorption leading to reduced serum levels of 25(0H)-vitamin D. d-a-Tocopheryl polyethylene glycol-1000 succinate (TPGS), a water-soluble form of vitamin E, forms micelles at low concentration. We evaluated the potential role of TPGS in enhancing vitamin D absorption in eight children (aged 5 mo to 19 y) with severe chronic cholestasis (three extrahepatic biliary atresia, three nonsyndromic intrahepatic cholestasis, and two Alagille syndrome). To evaluate vitamin D absorption, the subjects received vitamin D3 1000 IU/kg (maximum dose of 50 000 IU); they then received the same dose of vitamin Dg mixed with TPGS (25 IU/kg). Serial serum vitamin D3 levels and areas under the curve were measured. All patients had enhanced absorption of vitamin D when it was administered in a mixture with TPGS. Mean area under the curve for serum vitamin D3 was 403.0 -C 83.1 nmol x h/L (155.6 f 32.1 ng x h/mL), with a mean rise above baseline of 13.5 f 1.8 nmol/L (5.2 f 0.7 ng/mL) with vitamin D/TPGS compared with no rise when vitamin D was given alone (both p < 0.001). Seven patients have been followed for at least 3 mo while receiving the vitamin D/TPGS combination. Those with initially low serum 25(OH)-vitamin D levels (C37.5 nmol/L or 15 ng/mL) had normalization (range 37.5-146 nmol/L) within 1 mo, whereas those with initially normal levels remained normal. While the patients were receiving vitamin D/TPGS, serum vitamin E to total lipid ratio either normalized or remained normal. In conclusion, 1 ) TPGS enhances vitamin D absorption in infants and children with severe chronic cholestasis and 2) the enhanced absorption of both vitamins is sufficient to normalize or maintain adequate levels of serum 25(OH)-vitamin D and vitamin E to total lipid ratio. (Pediatr Res 31: 146-150,1992) Abbreviations 25(OH)D, 25-hydroxy-vitamin D TPGS, d-a-tocopheryl polyethylene glycol-1000 succinate
Almost all infants and children with chronic cholestasis have osteopenia. We evaluated the effect of orthotopic liver transplantation on bone mineral content and serum 25(OH)-vitamin D-[25(OH)D]-of nine infants and children (five girls; age, 6 to 21 mo at the time of orthotopic liver transplantation) with end-stage liver disease resulting from chronic cholestasis. We hypothesized that after orthotopic liver transplantation, decreased bone mineral content will recover and the serum 25(OH)D level will either normalize or remain normal in those who were previously vitamin D deficient or sufficient, respectively. All had subnormal bone mineral content before transplant. On long-term follow-up (> 4 mo) of seven patients, bone mineral content normalized in all between 6.5 and 19 mo after transplant, with a mean of 11.2 +/- 4.5 mo. In six patients with normal serum 25(OH)D levels before orthotopic liver transplantation, the serum 25(OH)D levels had declined markedly 1 to 2 mo after transplant, followed by return to normal by 3 to 6 mo. Low serum 25(OH)D levels (< 15 ng/ml) in three patients before orthotopic liver transplantation normalized after transplant. Although there was no correlation between bone mineral content and serum 25(OH)D level before transplant, sustained normal serum 25(OH)D and 1,25(OH)2D levels preceded or accompanied normalization of bone mineral content in the seven patients available for long-term follow-up. We conclude that (a) in infants and children younger than 2 yr with chronic cholestasis, bone mineral content normalizes approximately 11 mo after orthotopic liver transplantation. This normalization is preceded by a sustained period of normal serum 25(OH)D levels.(ABSTRACT TRUNCATED AT 250 WORDS)
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