Chromosome 11p15 paternal isodisomy in focal forms of neonatal hyperinsulinism

CONTEXT

Focal forms of congenital hyperinsulinism are due to a constitutional heterozygous mutation of paternal origin in the ABCC8 gene, more often than the KCNJ11 gene, located in the 11p15.1 region. This mutation is associated with the loss of the maternally inherited 11p15.1 to 11p15.5 region in the lesion. We investigated the possible occurrence of a compensatory duplication of the paternal 11p15.1-11p15.5 region.

MATERIALS AND METHODS

A combined immunohistochemistry and fluorescent in situ hybridization study on beta-cell interphase nuclei with probes covering two genes located in this region (ABCC8 and CDKN1C genes) was performed in four cases of focal forms of hyperinsulinism.

RESULTS

beta-Cells in the lesions of four cases of focal congenital hyperinsulinism were diploid for chromosomes 11 and 13. The 11p15.1 to 11p15.2 and 11p15.4 to 11p15.5 regions containing ABCC8 and CDKN1C genes, respectively, were present with two copies. Loss of the maternal allele was confirmed in these focal lesions with microsatellite markers flanking the ABCC8 and CDKN1C genes, whereas a heterozygous mutation in the ABCC8 gene was inherited from the father.

CONCLUSIONS

There is a duplication of the paternal allele on chromosome 11 in the focal forms of hyperinsulinism lesion. The paternal isodisomy observed rendered the beta-cells homozygous for ABCC8 mutation and harbored a K-channel defect in the lesion similar to that observed in diffuse forms of congenital hyperinsulinism.

Neonatal hyperinsulinism: clinicopathologic correlation

Neonatal hyperinsulinism is a life-threatening disease that, when treated by total pancreatectomy, leads to diabetes and pancreatic insufficiency. A more conservative approach is now possible since the separation of the disease into a nonrecurring focal form, which is cured by partial surgery, and a diffuse form, which necessitates total pancreas removal only in cases of medical treatment failure. The pathogenesis of the disease is now divided into K-channel disease (hyperinsulinemic hypoglycemia, familial [HHF] 1 and 2), which can mandate surgery, and other metabolic causes, HHF 3 to 6, which are treated medically in most patients. The diffuse form is inherited as a recessive gene on chromosome 11, whereas most cases of the focal form are caused by a sulfonylurea receptor 1 defect inherited from the father, which is associated with a loss of heterozygosity on the corresponding part of the mother's chromosome 11. The rare bifocal forms result from a maternal loss of heterozygosity specific to each focus. Paternal disomy of chromosome 11 is a rare cause of a condition similar to Beckwith-Wiedemann syndrome. A preoperative PET scan with fluorodihydroxyphenylalanine and perioperative frozen-section confirmation are the types of studies done before surgery when needed. Adult variants of the disease are less well defined at the present time.

Two Caucasian Families with the Hepatocyte Nuclear Factor-1Alpha Mutation Tyr218Cys

We report on the first two Caucasian families with the MODY3 HNF-1alpha mutation Tyr218Cys. Clinical and laboratory examinations are shown in detail. Patients with HNF-1alpha related MODY may develop the full spectrum of diabetic complications. Therefore, early detection of family members with MODY3 is warranted.

Focal segmental glomerulosclerosis associated with mitochondrial cytopathy

BACKGROUND

The nonspecific lesion of focal segmental glomerulosclerosis (FSGS) can occur as a primary disease or in a variety of secondary settings. In mitochondrial cytopathies (MCs), the phenotypic expression of the disease depends on the degree of cellular dysfunction, and this correlates with the proportion of abnormal mitochondrial DNA in the cells and the dependence of tissues on oxidative metabolism. The most common renal manifestation in MCs is tubular dysfunction; little has been reported about glomerular diseases.

METHODS

Cases of four adult patients with FSGS and MC are reported. Routine histology and mitochondrial DNA analysis were carried out on renal biopsies.

RESULTS

Family history and clinical manifestations in the four patients with FSGS suggested a diagnosis of MC. An A3243G transition in the mitochondrial DNA tRNA(leu(UUR)) was found in lymphocytes and kidney. Glomerular lesions of FSGS were associated with unusual hyaline lesions, which appeared to represent individual myocyte necrosis in afferent arterioles and small arteries.

CONCLUSION

FSGS is a renal manifestation of MCs. The renal lesion can precede other manifestations of the genetic disease by many years. The striking arteriolar lesions in these cases may have resulted in glomerular hypertension and hyperperfusion, leading to secondary epithelial cell abnormalities and, ultimately, FSGS. However, primary epithelial cell dysfunction caused by mitochondrial defects could not be ruled out on morphological grounds. MCs should be considered in cases of so-called primary FSGS, particularly if there is a familial history of diabetes, neuromuscular disorders, or deafness.

[The PROGENE study, the French project of genetic analysis of familial prostatic cancer: recruitment and analysis]

OBJECTIVES

To initiate a genetic linkage study in order to localize one or several predisposition gene(s) for hereditary prostatic cancer (PC), as various epidemiological studies have demonstrated a possible family aggregation in about 25% of cases. A family segregation study [14] has also shown that a genetic predisposition, with autosomal dominant transmission and high penetrance (88% at 85 years) could be responsible for 9% of all PC.

METHODS

A national collection of families with at least 2 cases of PC allowed: 1) identification of families with hereditary forms of PC, 2) creation of a constitutional DNA bank after collecting blood samples from subjects belonging to these families, and 3) a simulation study of genetic linkage analysis prior to microsatellite genotyping.

RESULTS

From July 1994 to September 1995, we included 67 families (180 cases of PC). Another 45 families are currently being included. 24 of these 67 families (89 PC, 54 survivors) satisfied at least one of the criteria defined in the study by CARTER et al. for hereditary forms of familial PC. Two families were also included as the 3 patients with PC were second degree relatives. A total of 26 families therefore presented a hereditary form, 18 of which (73 PC, 46 survivors) were considered to be informative for a genetic linkage study (lod score = 4 for theta = 0.001 with an 8 allele marker). The constitutional DNA of 271 individuals of these informative families was extracted from circulating cells obtained from blood samples, immortalized lymphocytes, and the genotyping was initiated for 216 microsatellite markers distributed throughout the genome, an average of every 20 cM.

CONCLUSION

Although the recruitment allowed us to identify many informative families for an inherited risk of PC, the predictive study suggested a high probability for localization of a predisposition gene by genetic linkage analysis. It would therefore be possible to identify, within the families concerned, the subjects carrying the genetic anomaly and consequently at high-risk of PC. Finally, the demonstration of the locus would allow cloning and identification of the gene (s) involved.