The Novel WT1 Gene Mutation p.H377N Associated to Denys-Drash Syndrome Mara Sanches Guaragna, BSc,* Fernanda Caroline Soardi, PhD,* Juliana Godoy Assumpc¸a ˜o, PhD,w Lı´lian de Jesus Girotto Zambaldi, BSc,w Izilda Aparecida Cardinalli, MD, PhD,w Jose ´ Andre´s Yunes, PhD,w Maricilda Palandi de Mello, PhD,* Silvia Regina Brandalise, MD, PhD,w z and Simone dos Santos Aguiar, MD, PhDw Summary: Denys-Drash syndrome (DDS, Online Mendelian Inheritance in Man number 194080) is a rare human developmental disease generally occurring in 46,XY individuals characterized by the combination of disorder of sex development, early onset nephropathy, and Wilms’ tumor (WT). DDS is mainly caused by mutations in the WT1 gene. This report describes a novel WT1 gene mutation in a DDS patient. Sequencing the WT1 gene revealed a heterozygous transversion CAT>AAT within exon 8, causing the substitution of an asparagine for a histidine at residue 377. The p.H377N mutation is predicted to diminish the WT1 protein DNA-binding affinity as it might disrupt the normal zinc finger 2 conformation. Key Words: Denys-Drash syndrome, Wilms’ Tumor, WT1 gene, disorder of sex development, mutation (J Pediatr Hematol Oncol 2010;32:486–488) D enys-Drash syndrome (DDS, Online Mendelian In- heritance in Man number 194080) is a complex autosomal dominant congenital disorder consisting of genitourinary abnormalities. Generally, it is associated with XY disorders of sex development, early onset nephro- pathy, and presents high risk of developing Wilms’ tumor. 1,2 DDS is mainly caused by mutations in the WT1 gene. WT1 mRNA and protein are predominantly pro- duced in the developing fetal kidneys, genital ridge, and gonads. 3,4 The human WT1 gene is located on chromosome 11 (11p13), contains 10 exons, and encodes a protein of 45 to 49 kda. It encodes a zinc finger transcription factor that has been reported to regulate the expression of several genes in developing gonads and kidneys. 5 Exons 1 to 6 are involved in transcriptional regulation and protein homo- dimerization, whereas exons 7 to 10 encode the 4 zinc fingers of the DNA-binding domains. 6,7 WT1 can act as either a transcription activator or repressor, depending on both the promoter region of the target gene and the cellular context. 8 The majority of WT1 mutations in patients with DDS are de novo point mutations clustered in exons 8 and 9. This region is considered a hot spot for mutations that affect zinc finger 2 or 3 structure. Up to now there are 33 different WT1 mutations described in DDS, all of them resulting in amino acid substitutions or frameshift muta- tions that lead to premature stop codons. Most DDS patients with the 46,XY karyotype present with ambiguous genitalia (such as bilateral chryptorchid- ism, hypospadia) or female phenotype. Normal females with 46,XY karyotype and gonadal dysgenesis can be easily underestimated because their normal external geni- talia, and hence their risk for developing Wilms’ tumor may be neglected. 9 Nephropathy resulting from focal or diffuse mesangial sclerosis, usually develops between 2 months and 2 years of age, and presents with progres- sive renal failure or nephrotic syndrome. 10 The develop- ment of Wilms’ tumor in DDS patients occurs earlier than in the general population and is more often bilateral or multiple owing to the constitutional WT1 predisposing mutation. 11 In this report we describe the novel WT1 gene mutation p.H377N identified in a child diagnosed with DDS. CASE REPORT The child was born at term after an uneventful pregnancy and was registered as a girl. The child developed normally up to 3 months of age, when presented with urinary infection and oliguria, which evolved to renal insufficiency. Peritoneal dialysis was initiated but was suspended after 3 months owing to a peritoneal infection. At 6 months of age hemodialysis was initiated. At 10 months of age the patient presented with urinary infection and sepsis. Tomography scan analysis showed a bilateral renal tumor (Fig. 1A) and the patient was referred to our service (Centro Infantil Boldrini, Campinas, Sao Paulo, Brazil). Tumor biopsy and histopathologic examination (Figs. 1B, C) evidenced the Wilms’ tumor. Molecular analysis was not accomplished in tumor material. Owing to genital ambiguity, cytogenetic analysis was performed, revealing a 46,XY karyotype. The patient died at 10 months of age as a result of peritoneal fungal infection. Copyright r 2010 by Lippincott Williams & Wilkins Received for publication December 3, 2009; accepted April 20, 2010. From the *Laborato´rio de Gene´tica Molecular Humana, Centro de Biologia Molecular e Engenharia Gene´tica, Universidade Estadual de Campinas; wLaborato´rio de Biologia Molecular, Centro Infantil Boldrini; and zDepartamento de Pediatria, Universidade Estadual de Campinas, Campinas, Sao Paulo, Brasil. Supported by grants from Fundac ¸a˜o de Amparo a` Pesquisa do Estado de Sa˜o Paulo (FAPESP), Coordenac ¸a˜o de Aperfeic ¸oamento de Pessoal de Nı´vel Superior (CAPES), and Conselho Nacional de Desenvolvimento Cientı´fico e Tecnolo´gico (CNPq). Reprints: Simone dos Santos Aguiar, MD, PhD, Centro Infantil Boldrini, Rua Dr Gabriel Porto 1270, 13083-210 Campinas, Sao Paulo, Brazil (e-mail: simone@boldrini.org.br). CLINICAL AND LABORATORY OBSERVATIONS 486 | www.jpho-online.com J Pediatr Hematol Oncol  Volume 32, Number 6, August 2010