Lucia Galli

MECP2 mutation in male patients with non‐specific X‐linked mental retardation

In contrast to the preponderance of affected males in families with X‐linked mental retardation, Rett syndrome (RTT) is a neurological disorder occurring almost exclusively in females. The near complete absence of affected males in RTT families has been explained by the lethal effect of an X‐linked gene mutation in hemizygous affected males. We report here on a novel mutation (A140V) in the MECP2 gene detected in one female with mild mental retardation. In a family study, the A140V mutation was found to segregate in the affected daughter and in four adult sons with severe mental retardation. These results indicate that MECP2 mutations are not necessarily lethal in males and that they can be causative of non‐specific X‐linked mental retardation.

Novel PTEN mutations in neurodevelopmental disorders and macrocephaly.

Somatic mutations of the phosphatase and tensin (PTEN) gene have been frequently detected in many types of human cancer. However, germline mutations can determine multiple hamartoma syndromes and, as more recently ascertained, syndromes clinically characterized by autism associated with macrocephaly. To determine whether germline mutations of PTEN may lead to different phenotypes, we screened all the nine exons of the PTEN gene in 40 patients with neurodevelopmental disorders, with or without features of autism spectrum disorder, associated with macrocephaly. Three novel de novo missense mutations were found (p.H118P, p.Y176C, p.N276S) in two severely mentally retarded patients with autism and in a subject with neurodevelopmental disorders without autistic features. Our results provide evidence that PTEN germline mutations may sustain a more wide phenotypical spectrum than previously suggested.

Phenotypic and molecular characterisation of the Aarskog–Scott syndrome: a survey of the clinical variability in light of FGD1 mutation analysis in 46 patients

Faciogenital dysplasia or Aarskog–Scott syndrome (AAS) is a genetically heterogeneous developmental disorder. The X-linked form of AAS has been ascribed to mutations in the FGD1 gene. However, although AAS may be considered as a relatively frequent clinical diagnosis, mutations have been established in few patients. Genetic heterogeneity and the clinical overlap with a number of other syndromes might explain this discrepancy. In this study, we have conducted a single-strand conformation polymorphism (SSCP) analysis of the entire coding region of FGD1 in 46 AAS patients and identified eight novel mutations, including one insertion, four deletions and three missense mutations (19.56% detection rate). One mutation (528insC) was found in two independent families. The mutations are scattered all along the coding sequence. Phenotypically, all affected males present with the characteristic AAS phenotype. FGD1 mutations were not associated with severe mental retardation. However, neuropsychiatric disorders, mainly behavioural and learning problems in childhood, were observed in five out of 12 mutated individuals. The current study provides further evidence that mutations of FGD1 may cause AAS and expands the spectrum of disease-causing mutations. The importance of considering the neuropsychological phenotype of AAS patients is discussed.

Phylogenetically Related Argentinean and Australian Escherichia coli O157 Isolates Are Distinguished by Virulence Clades and Alternative Shiga Toxin 1 and 2 Prophages

ABSTRACT Shiga toxigenic Escherichia coli O157 is the leading cause of hemolytic uremic syndrome (HUS) worldwide. The frequencies of stx genotypes and the incidences of O157-related illness and HUS vary significantly between Argentina and Australia. Locus-specific polymorphism analysis revealed that lineage I/II (LI/II) E. coli O157 isolates were most prevalent in Argentina (90%) and Australia (88%). Argentinean LI/II isolates were shown to belong to clades 4 (28%) and 8 (72%), while Australian LI/II isolates were identified as clades 6 (15%), 7 (83%), and 8 (2%). Clade 8 was significantly associated with Shiga toxin bacteriophage insertion (SBI) type stx 2 (locus of insertion, argW) in Argentinean isolates (P < 0.0001). In Argentinean LI/II strains, stx 2 is carried by a prophage inserted at argW, whereas in Australian LI/II strains the argW locus is occupied by the novel stx 1 prophage. In both Argentinean and Australian LI/II strains, stx 2c is almost exclusively carried by a prophage inserted at sbcB. However, alternative q 933- or q 21-related alleles were identified in the Australian stx 2c prophage. Argentinean LI/II isolates were also distinguished from Australian isolates by the presence of the putative virulence determinant ECSP_3286 and the predominance of motile O157:H7 strains. Characteristics common to both Argentinean and Australian LI/II O157 strains included the presence of putative virulence determinants (ECSP_3620, ECSP_0242, ECSP_2687, ECSP_2870, and ECSP_2872) and the predominance of the tir255T allele. These data support further understanding of O157 phylogeny and may foster greater insight into the differential virulence of O157 lineages.

Mutations in the glucose-6-phosphate transporter (G6PT) gene in patients with glycogen storage diseases type 1b and 1c

Glycogen storage diseases type 1 (GSD 1) are a group of autosomal recessive disorders characterized by impairment of terminal steps of glycogenolysis and gluconeogenesis. Mutations of the glucose‐6‐phosphatase gene are responsible for the most frequent form of GSD 1, the subtype 1a, while mutations of the glucose‐6‐phosphate transporter gene (G6PT) have recently been shown to cause the non 1a forms of GSD, namely the 1b and 1c subtypes. Here, we report on the analysis by single‐stranded conformation polymorphism (SSCP) and/or DNA sequencing of the exons of the G6PT in 14 patients diagnosed either as affected by the GSD 1b or 1c subtypes. Mutations in the G6PT gene were found in all patients. Four of the detected mutations were novel mutations, while the others were previously described. Our results confirm that the GSD 1b and 1c forms are due to mutations in the same gene, i.e. the G6PT gene. We also show that the same kind of mutation can be associated or not with evident clinical complications such as neutrophil impairment. Since no correlation between the type and position of the mutation and the severity of the disease was found, other unknown factors may cause the expression of symptoms, such as neutropenia, which dramatically influence the severity of the disease.

A mutation in the pleckstrin homology (PH) domain of the FGD1 gene in an Italian family with faciogenital dysplasia (Aarskog–Scott syndrome)

Aarskog–Scott Syndrome (AAS) is an X‐linked disorder characterised by short stature and multiple facial, limb and genital abnormalities. A gene, FGD1, altered in a patient with AAS phenotype, has been identified and found to encode a protein with homology to Rho/Rac guanine nucleotide exchange factors (Rho/Rac GEF). However, since this original report on identification of a mutated FGD1 gene in an AAS patient, no additional mutations in the FGD1 gene have been described. We analysed 13 independent patients with clinical diagnosis of AAS. One patient presented a mutation that results in a nucleotide change in exon 10 of the FGD1 gene (G2559>A) substituting a Gln for Arg in position 610. The mutation was found to segregate with the AAS phenotype in affected males and carrier females in the family of this patient. Interestingly, Arg‐610 is located within one of the two pleckstrin homology (PH) domains of the FGD1 gene and it corresponds to a highly conserved residue which has been involved in InsP binding in PH domains of other proteins. The same residue is often mutated in the Brutons tyrosine kinase (Btk) gene in patients with an X‐linked agammaglobulinemia. The Arg610Gln mutation represents the first case of a mutation in the PH domain of the FGD1 gene and additional evidence that mutations in PH domains can be associated to human diseases.

Shiga toxin-producing Escherichia coli in beef retail markets from Argentina

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens that cause mild or serious diseases and can lead to people death. This study reports the prevalence and characteristics of STEC O157 and non-O157 in commercial ground beef and environmental samples, including meat table, knife, meat mincing machine, and manipulator hands (n = 450) obtained from 90 retail markets over a nine-month period. The STEC isolates were serotyped and virulence genes as stx (Shiga toxin), rfbO157] (O157 lipopolysaccharide), fliCH7 (H7 flagellin), eae (intimin), ehxA (enterohemolysin) and saa (STEC autoagglutinating adhesin), were determined. STEC O157 were identified in 23 (25.5%) beef samples and 16 (4.4%) environmental samples, while STEC non-O157 were present in 47 (52.2%) and 182 (50.5%), respectively. Among 54 strains isolated, 17 were STEC O157:H7 and 37 were STEC non-O157. The prevalent genotype for O157 was stx2/eae/ehxA/fliCH7 (83.4%), and for STEC non-O157 the most frequent ones were stx1/stx2/saa/ehxA (29.7%); stx2 (29.7%); and stx2/saa/ehxA (27%). None of the STEC non-O157 strains were eae-positive. Besides O157:H7, other 20 different serotypes were identified, being O8:H19, O178:H19, and O174:H28 the prevalent. Strains belonging to the same serotype could be isolated from different sources of the same retail market. Also, the same serotype could be detected in different stores. In conclusion, screening techniques are increasingly sensitive, but the isolation of STEC non-O157 is still a challenge. Moreover, with the results obtained from the present work, although more studies are needed, cross-contamination between meat and the environment could be suspected.

Mosaicism for full mutation and normal-sized allele of the FMR1 gene: a new case.

The main mutation in fragile X patients is the expansion of the CGG repeat in the first exon of the FMR1 gene, associated with hypermethylation of the proximal CpG island. An increasing number of atypical cases have been reported showing the coexistence of full mutation and premutated or normal-sized alleles. These genotypes are more difficult to detect, and if a PCR strategy alone is adopted, they can be incorrectly identified. We report on a fragile X man with severe phenotype and mosaicism for full mutation and a (CGG)7 normal allele, the shortest fragment reported as yet in mosaics. This case of mosaicism, as other similar cases previously reported, suggests that the normal-length allele can derive from a deletion during the same early stage of development in which the full mutation expansion also arose.

Attention-deficit/hyperactivity disorder (ADHD) and variable clinical expression of Aarskog–Scott syndrome due to a novel FGD1 gene mutation (R408Q)

Mutations of the FGD1 gene are responsible for a significant proportion of patients with Aarskog–Scott syndrome (AAS), an X‐linked disorder characterized by short stature, brachydactyly, urogenital abnormalities, and a typical dysmorphic facial appearance. Although mental retardation does not occur significantly in AAS, this condition has been described associated with various degrees of mental impairment and/or behavioral disorders in some patients. In particular, attention deficit hyperactivity disorder (ADHD) is reported as a common characteristic of AAS. However, AAS/ADHD reported patients have been only clinically described, and diagnosis never has been confirmed on molecular basis. We present here a unique case of a 16‐years‐old patient presenting with ADHD, lower intelligence quotient, and dysmorphic features. Although the clinical features were not completely typical of AAS, genetic analysis demonstrated a novel FGD1 missense mutation (R408Q). The case we report confirms the highly variable expressivity of AAS and first documents that the FGD1 gene may play a role in ADHD susceptibility. We suggest that FGD1 analysis may be adequate in ADHD patients who exhibit dysmorphic features suggestive of AAS, also in the absence of the full phenotypical spectrum.

SCN1A (2528delG) novel truncating mutation with benign outcome of severe myoclonic epilepsy of infancy

The epileptic syndrome related to mutations in the SCN1A gene includes benign febrile seizures (FS), the more variable phenotype FS+, and severe myoclonic epilepsy in infancy (SMEI) or Dravet syndrome, one of the most severe types of infant epilepsy, which is resistant to drugs.1 The clinical spectrum related to mutations of the SCN1A gene (chromosome 2q) has been divided according to the type of seizure and CNS impairment into four categories from the lightest (benign FS) to the most severe (classic type SMEI).2 Evidence suggests that a severe disturbance of the function of the SCN1A gene is a major cause of SMEI, and that FS, FS+ (even with other types of seizures), and the milder and classic types of SMEI form a continuum of mutations in the α subunit of SCN1A . Severe de novo mutations, such as truncating mutations, have been reported in SMEI.2,3 We report a patient with SMEI with a benign outcome, in whom the clinical picture changed from SMEI in infancy to FS+ in adolescence and was associated with a novel, de novo truncating mutation of the SCN1A gene.nnThe patient was a 13-year-old …