Long-term follow-up of childhood-onset hypopituitarism in patients with the PROP-1 gene mutation

OBJECTIVE: The PROP-1 gene mutation is a rare disorder leading to combined pituitary hormone deficiencies over time. The aim was to analyze the clinical picture of 40 years of an almost untreated PROP-1 gene mutation. METHODS: We describe the clinical and hormonal data of 2 brothers from childhood to adulthood as well as imaging procedures (MRI of the pituitary gland, bone mineral density by QCT and DPX). The PROP-1 gene mutation (301-302delAG) was confirmed by DNA sequencing. RESULTS: Although long-standing untreated hypopituitarism was present, there was normal physical and professional activity. Bone mineral density was low only in 1 patient. Adrenocortical deficiency occurred late at 45 and 39 years. CONCLUSIONS: The biological evolution of the PROP-1 gene mutation illustrates the importance of continuous care for these patients. Hormonal deficiencies do not necessarily lead to the same phenotype as is obvious in differences of bone age and bone mineral density.     

X-linked recessive combined pituitary hormone deficiency is mapped to Xp22.3-Xp11 in a Chinese family

Genetic mutations have been identified in a modest proportion of patients with combined pituitary hormone deficiency (CPHD). We reported a 3-generation family consisting of 18 members, including 5 affected males (the proband, his 2 brothers, his cousin, and his maternal uncle; III1–III4, II8) suffered with CPHD. MRI of the pituitary gland showed hypoplasia of the pituitary gland in affected members. By 19 STR markers and linkage analysis, we found that the disease gene localized between the DXS987 and DXS1226 markers (LOD score = 2.408, θ = 0). All affected male patients inherited the same haplotype from the female carrier (I4). The proband's mother (II4) and her sister (II3, II6) were obligate female carriers. However, the unaffected males (II₇, II₉) in the family did not have this haplotype. These observations confirm a new X-linked recessive inherited disease in a Chinese family with CPHD and the pathogenic gene is mapped to Xp22.1–Xp11.     

A new mutation of 5-alpha-reductase type 2 (A62E) in a large Egyptian kindred

OBJECTIVE: To describe the clinical, biological and molecular data in a large Egyptian kindred with 5alpha-reductase deficiency. PATIENTS AND METHODS: Three patients with ambiguous genitalia were referred at the ages of 20, 9 and 2 years, respectively. In all cases, parents were first cousins. Basal and post-HCG stimulation plasma levels of testosterone and dihydrotestosterone were determined. Direct sequencing and restriction site analysis were applied for patient and family study. RESULTS: A homozygous alanine to glutamic acid substitution at position 62 (A62E) was found in the three patients. The parents and two XX sisters were heterozygous while a third XX sibling was normal. CONCLUSION: We report a new mutation of the 5alpha-reductase type 2 gene. The presence of this mutation in all studied patients and their parents suggests its causative role in 5alpha-reductase deficiency. Identification of the mutation enabled genetic counselling for three XX individuals.     

Multiple identification of a particular type of hereditary C1q deficiency in the Turkish population: review of the cases and additional genetic and functional analysis

Complete selective deficiencies of the complement component C1q are rare genetic disorders that are associated with recurrent infections and a high prevalence of lupus erythematosus-like symptoms. All C1q deficiencies studied at the genetic level revealed single-base mutations leading to termination codons, frameshifts or amino acid exchanges and these were thought to be responsible for the defects as no other aberrations were found. One particular mutation, leading to a stop codon in the C1qA gene, was first identified in members of a Gypsy family from the Slovak Republic. The same mutation has been found in all cases of C1q deficiency from Turkey that have been investigated. Here we present the results of genetic analysis of the C1q genes from three families and give information on further C1q-deficient members of two families that have not been reported elsewhere. Reviewing all cases of C1q deficiency from Turkey prompted us to hypothesize that one particular defective allele is present in the population of southeast Europe and Turkey. With a novel polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis and allele-specific PCR we are able to detect even asymptomatic, heterozygous carriers of the mutation, which will enable genetic counseling of the affected individuals. Received: 19 November 1996 / Accepted: 20 January 1997     

Null mutations in the N-acetylglutamate synthase gene associated with acute neonatal disease and hyperammonemia

N-acetylglutamate synthase (NAGS) is a mitochondrial enzyme that catalyzes the formation of N-acetylglutamate, an essential allosteric activator of carbamyl phosphate synthetase I, the first enzyme of the urea cycle. Liver NAGS deficiency has previously been found in a small number of patients with hyperammonemia. The mouse and human NAGS genes have recently been cloned and expressed in our laboratory. We searched for mutations in the NAGS gene of two families with presumed NAGS deficiency. The exons and exon/intron boundaries of the NAGS gene were sequenced from genomic DNA obtained from the parents of an infant from the Faroe Islands who died in the neonatal period and from two Hispanic sisters who presented with acute neonatal hyperammonemia. Both parents of the first patient were found to be heterozygous for a null mutation in exon 4 (TGG-->TAG, Trp324Ter). Both sisters from the second family were homozygous for a single base deletion in exon 4 (1025delG) causing a frameshift and premature termination of translation. The finding of deleterious mutations in the NAGS gene confirms the genetic origin of NAGS deficiency. This disorder can now be diagnosed by DNA testing allowing for carrier detection and prenatal diagnosis.     

Dihydropyrimidine dehydrogenase (DPD) deficiency: identification and expression of missense mutations C29R, R886H and R235W

Dihydropyrimidine dehydrogenase (DPD) deficiency (McKusick 274270) is an autosomal recessive disease characterized by thymine-uraciluria in homozygous-deficient patients and associated with a variable clinical phenotype. Cancer patients with this defect should not be treated with the usual dose of 5-fluorouracil because of the expected lethal toxicity. In addition, heterozygosity for mutations in the DPD gene increases the risk of toxicity in cancer patients treated with this drug. Sequence analysis in a patient with complete DPD deficiency, previously shown to be heterozygous for the ΔC1897 frameshift mutation, revealed the presence of a novel missense mutation, R235W. Expression of this novel mutation and previously identified missense mutations C29R and R886H in Escherichia coli showed that both C29R and R235W lead to a mutant DPD protein without significant residual enzymatic activity. The R886H mutation, however, resulted in about 25% residual enzymatic activity and is unlikely to be responsible for the DPD-deficient phenotype. We show that the E. coli expression system is a valuable tool for examining DPD enzymatic variants. In addition, two new patients who were both heterozygous for the C29R mutation and the common splice donor site mutation were identified. Only one of these patients showed convulsive disorders during childhood, whereas the other showed no clinical phenotype, further illustrating the lack of correlation between genotype and phenotype in DPD deficiency. Received: 20 June 1997 / Accepted: 26 August 1997     

X-linked mental retardation with seizures and carrier manifestations is caused by a mutation in the creatine-transporter gene (SLC6A8) located in Xq28

A family with X-linked mental retardation characterized by severe mental retardation, speech and behavioral abnormalities, and seizures in affected male patients has been found to have a G1141C transversion in the creatine-transporter gene SLC6A8. This mutation results in a glycine being replaced by an arginine (G381R) and alternative splicing, since the G-->C transversion occurs at the -1 position of the 5' splice junction of intron 7. Two female relatives who are heterozygous for the SLC6A8 mutation also exhibit mild mental retardation with behavior and learning problems. Male patients with the mutation have highly elevated creatine in their urine and have decreased creatine uptake in fibroblasts, which reflects the deficiency in creatine transport. The ability to measure elevated creatine in urine makes it possible to diagnose SLC6A8 deficiency in male patients with mental retardation of unknown etiology.     

The first nuclear-encoded complex I mutation in a patient with Leigh syndrome.

Nicotinamide adenine dinucleotide (NADH):ubiquinone oxidoreductase (complex I) is the largest multiprotein enzyme complex of the respiratory chain. The nuclear-encoded NDUFS8 (TYKY) subunit of complex I is highly conserved among eukaryotes and prokaryotes and contains two 4Fe4S ferredoxin consensus patterns, which have long been thought to provide the binding site for the iron-sulfur cluster N-2. The NDUFS8 cDNA contains an open reading frame of 633 bp, coding for 210 amino acids. Cycle sequencing of amplified NDUFS8 cDNA of 20 patients with isolated enzymatic complex I deficiency revealed two compound heterozygous transitions in a patient with neuropathologically proven Leigh syndrome. The first mutation was a C236T (P79L), and the second mutation was a G305A (R102H). Both mutations were absent in 70 control alleles and cosegregated within the family. A progressive clinical phenotype proceeding to death in the first months of life was expressed in the patient. In the 19 other patients with enzymatic complex I deficiency, no mutations were found in the NDUFS8 cDNA. This article describes the first molecular genetic link between a nuclear-encoded subunit of complex I and Leigh syndrome.     

Biochemical and genetic studies of four patients with pyruvate dehydrogenase E1α deficiency

We report studies of four patients with pyruvate dehydrogenase complex (PDH) deficiency caused by mutations in the E1α subunit. Two unrelated male patients presented with Leigh syndrome and a R263G missense mutation in exon 8. This mutation has previously been described in males with the same phenotype. The two other patients had different novel mutations: (1) an 8-bp deletion at the C-terminus (exon 11) was found in one allele of a young girl suffering from microcephaly and (2) a C88S missense mutation (exon 3) in a boy who only presented with motor neuropathy. These mutations were not found in the mothers of any of the four cases. Immunoblot analysis revealed decreased immunoreactivity for the E1α and E1β subunits in three out of the four patients. These findings confirm that: (1) PDH deficiencies are genetically heterogeneous, (2) the R263G mutation is more frequent in male cases than are other mutations and this amino acid is a hot spot for gene mutations, (3) the last eight amino acids may be important for the conformation of the tetrameric E1-PDH enzyme, and (4) the amino acids at positions 88, 263 and 382–387 are essential for the linking of the α subunit with the β subunit and for the activity of the holoenzyme. Received: 28 October 1996 / Revised: 13 January 1997     

Toward genotype phenotype correlations in GFM1 mutations

Multiple respiratory chain deficiencies represent a common cause of mitochondrial diseases. We report two novel GFM1 mutations in two unrelated patients with encephalopathy and liver failure respectively. The first patient had intrauterine growth retardation, seizures, encephalopathy and developmental delay. Brain MRI showed hypoplasia of the vermis and severe pontine atrophy of the brainstem that were similar to those reported in patients with mitochondrial translation deficiencies. The second patient had liver failure with hypoglycemia. Respiratory chain analysis showed a complex IV deficiency in muscle of both patients. A 10K SNP genotyping detected several regions of homozygosity in the two patients. In vitro translation deficiency prompted us to study genes involved in mitochondrial translation. Therefore, we sequenced the GFM1 gene, encoding the mitochondrial translation factor EFG1, included in a shared homozygous region and identified two different homozygous mutations (R671C and L398P). Modeling studies of EFG1 protein suggested that the R671C mutation disrupts an inter-subunit interface and could locally destabilize the mutant protein. The second mutation (L398P) disrupted the H-bond network in a rich-beta-sheet domain, and may have a dramatic effect on local structure. GFM1 mutations have been seldom reported and are associated with different clinical presentation. By modeling the structure of the protein and the position of the various mutations we suggest that the clinical phenotypes of the patients could be related to the localization of the mutations.     

Complete complement components C4A and C4B deficiencies in human kidney diseases and systemic lupus erythematosus

Although a heterozygous deficiency of either complement component C4A or C4B is common, and each has a frequency of approximately 20% in a Caucasian population, complete deficiencies of both C4A and C4B proteins are extremely rare. In this paper the clinical courses for seven complete C4 deficiency patients are described in detail, and the molecular defects for complete C4 deficiencies are elucidated. Three patients with homozygous HLA A24 Cw7 B38 DR13 had systemic lupus erythematosus, mesangial glomerulonephritis, and severe skin lesions or membranous nephropathy. Immunofixation, genomic restriction fragment length polymorphisms, and pulsed field gel electrophoresis experiments revealed the presence of monomodular RP-C4-CYP21-TNX (RCCX) modules, each containing a solitary, long C4A mutant gene. Sequencing of the mutant C4A genes revealed a 2-bp, GT deletion in exon 13 that leads to protein truncation. The other four patients with homozygous HLA A30 B18 DR7 had SLE, severe kidney disorders including mesangial or membranoproliferative glomerulonephritis, and/or Henoch Schoenlein purpura. Molecular genetic analyses revealed an unusual RCCX structure with two short C4B mutant genes, each followed by an intact gene for steroid 21-hydroxylase. Nine identical, intronic mutations were found in each mutant C4B. In particular, the 8127 g-->a mutation present at the donor site of intron 28 may cause an RNA splice defect. Analyses of 12 complete C4 deficiency patients revealed two hot spots of deleterious mutations: one is located at exon 13, the others within a 2.6-kb genomic region spanning exons 20-29. Screening of these mutations may facilitate epidemiologic studies of C4 in infectious, autoimmune, and kidney diseases.     

A novel nonsense mutation of the GTP cyclohydrolase I gene in a family with dopa-responsive dystonia

We report a new nonsense mutation in the GTP cyclohydrolase I (GCH1) gene in a family with dopa-responsive dystonia. Two sisters and three children of the sisters are affected. The exons of the GCH1 gene were amplified by PCR and sequenced. The substitution of thymine for cytosine at nucleotide position 142 causing a nonsense mutation (Q48X) in exon 1 was identified in all of the five affected patients. There were three asymptomatic carriers of the mutation in the family.