WT1 and Sox11 regulate synergistically the promoter of the Wnt4 gene that encodes a critical signal for nephrogenesis.

Wnt4, a member of the Wnt superfamily of signaling molecules, is critical for mammalian kidney development, since nephrogenesis fails in its absence, while Wnt4 signaling induces mesenchyme-to-epithelium transition and associated tubulogenesis in the uninduced mesenchymal cells in the classic transfilter model. The factors that promote Wnt4 gene expression during kidney development are largely unknown, however. We addressed the upstream regulators of the Wnt4 gene and describe here the transcription factors WT1 and Sox11 as candidate molecules in the control of gene expression. We found that WT1/Sox11 regulate Wnt4 promoter expression in a synergistic fashion in an embryonic kidney mesenchyme-derived cell line model. The transcription complex containing WT1/Sox11 was immunoprecipitated from embryonic kidney cells with Sox11 antibodies, suggesting their presence in the same complex. Dominant negative forms of WT1, namely P129L and F154S mutants, inhibited Wnt4 expression, but this inhibition was not influenced by the presence of wild-type Sox11. The mutant WT1 forms were similarly incapable of interacting with Sox11, as judged by reporter studies. The spatio-temporal expression pattern of wt1 and sox11 overlaps with that of Wnt4 in the early Xenopus pronephros. Morpholino-mediated knockdown of either wt1 or sox11 inhibited Wnt4 expression in the prospective pronephros of the Xenopus embryos. We propose that Sox11 represents a synergistic factor for WT1 in regulating the Wnt4 gene expression that is critical for nephrogenesis during kidney ontogeny.

Conditional expression of Lodavin, an avidin-tagged LDL receptor, for biotin-mediated applications in vivo.

Lodavin represents an engineered fusion protein that consists of a cytoplasmic and a transmembrane domain of the human low-density lipoprotein receptor coupled to an extracellular avidin monomer. Biotinylated compounds have been successfully targeted to Lodavin-expressing cells that have been transduced by a Lodavin-containing virus, and the targeting is based on the high affinity between biotin and avidin. We engineered a Rosa26 (R26R) knock-in Lodavin mouse to develop biotin-based applications such as targeted drug delivery, cell purification, and tissue imaging in vivo. A cDNA encoding Lodavin was inserted downstream of a floxed ßgeo resistance gene in the R26R locus in embryonic stem cells, and a germ line-derived R26RLodavin mouse line was generated. Efficient removal of the floxed ßgeo cassette and conditional activation of Lodavin expression was achieved as a result of crossing the R26RLodavin mice with HoxB7-Cre, Wnt4-Cre, or Tie1-Cre mice. In summary, the R26RLodavin mouse line may provide a useful tool for testing and developing applications with the aid of avidin and biotin interaction.

Wnt signaling in kidney development and disease.

The Wnt gene family, which encodes secreted growth and differentiation factors, has been implicated in kidney organogenesis. The Wnts control both ureteric bud development and signaling, but they also serve as inductive factors to regulate nephrogenesis in the mesenchcymal cells. Several of the Wnt genes are expressed in the developing kidney, and gene knock-out studies have revealed specific developmental functions for these. Consistent with this, changes in Wnt ligands and pathway components are associated with many kidney diseases, including kidney cancers, renal fibrosis, cystic kidney diseases, acute renal failure, diabetic nephropathy and ischaemic injury. It is these associations of the Wnt signaling system with kidney development and kidney diseases that form to topic of this review.

Heart surgery in infants with hemophilia.

We describe 2 infants with hemophilia A who had heart surgery under cardiopulmonary bypass with factor VIII replacement therapy, and we recommend a guideline for factor VIII support for cardiac surgery. One child had repair of total anomalous pulmonary venous connection. The second had cardiac catheterization followed by repair of ventricular septal defect and total anomalous pulmonary venous connection. Close collaboration between hematologist, laboratory, cardiologist, and cardiac surgeon is crucial in successful management of coagulation abnormalities during and after surgery.

A case of long QT syndrome associated with familial occurrence of persistent patency of the arterial duct.

We describe an occurrence of long QT syndrome in association with persistent patency of the arterial duct in members of a family. Patency of the arterial duct was diagnosed in family members of 4 successive generations. The index case had long QT syndrome associated with such a patent duct. Another patient had long QT syndrome, but associated with a ventricular septal defect. We postulate that there may be a common genetic mechanism for long QT syndrome and persistent patency of the arterial duct.

New outpatient referrals to a tertiary paediatric cardiac centre: evidence of increasing workload and evolving patterns of referral.

OBJECTIVES: To assess the volume and range of diagnosis in new patients referred to paediatric cardiac outpatient clinics. METHODS: Data was collected prospectively, using a proforma completed at all outpatient clinics over a period of three months. RESULTS: There were 526 new referrals, representing an increase of almost one-fifth compared to 5 years ago. Of the referrals, 78 percent came from hospital doctors, and 22 percent from general practitioners, with 221 of those referred being infants. A heart murmur was the most common reason for referral, representing almost two-thirds of cases. In 372 patients referred (71 percent), the heart was discovered to be structurally normal. The proportion of patients with normal hearts referred by general practitioners and hospital doctors were 81 percent, and 68 percent, respectively (p less than 0.004). There was considerable variation in the pattern of referral between doctors working in different hospitals. CONCLUSION: New referrals to centres dealing with congenital cardiac malformations are increasing alarmingly, with the majority of the children referred having normal hearts. This increase in demand for specialist services has important implications for resources and training.