High TGM1 Allelic Heterogeneity causing Lamellar ichthyosis in a small geographic area in South Mexico: Another Example of the "Réunion Paradox".

Lamellar ichthyosis (LI) is an autosomal recessive congenital ichthyosis characterized by generalized dry skin and severe scaling. It is caused by biallelic mutations in the TGM1 gene, however molecular data from non-Caucasian populations are limited. Results of genetic-molecular analysis of a group of LI pedigrees originating from two close small populations from south Mexico are presented. LI affected individuals belonging to 9 apparently unrelated families were studied. Exome sequencing or Sanger sequencing in probands from each family was carried out. Furthermore, DNA from 294 unaffected subjects from one of the communities were Sanger sequenced to determine the carrier frequency of the c.427C > T TGM1 variant. Five different TGM1 pathogenic variants, either in homozygous or in compound heterozygous state, were demonstrated in affected subjects. The two most common variants were c.427C > T (p.Arg143Cys) and c.1159+1G > T. A novel c.1645+1G > T TGM1 pathogenic allele was recognized. Carrier frequency analysis identified a total of 23 individuals heterozygous for the c.427C > T variant, predicting a prevalence of 78 carriers per 1000 inhabitants in the community. A high TGM1 allelic heterogeneity with 5 different LI-causing alleles in a limited geographic area was demonstrated. While the occurrence of homozygosity for a founder mutation is expected in small populations with high frequency of a particular autosomal recessive disorder, the occurrence of multiple pathogenic alleles has been previously described, a situation known as the Reúnion paradox. Our results expand the current knowledge of the mutational spectrum of TGM1-linked LI.

Case report: Disease phenotype associated with simultaneous biallelic mutations in ABCA4 and USH2A due to uniparental disomy of chromosome 1.

Inherited retinal diseases (IRDs) represent a spectrum of clinically and genetically heterogeneous disorders. Our study describes an IRD patient carrying ABCA4 and USH2A pathogenic biallelic mutations as a result of paternal uniparental disomy (UPD) in chromosome 1. The proband is a 9-year-old girl born from non-consanguineous parents. Both parents were asymptomatic and denied family history of ocular disease. Clinical history and ophthalmologic examination of the proband were consistent with Stargardt disease. Whispered voice testing disclosed moderate hearing loss. Next-generation sequencing and Sanger sequencing identified pathogenic variants in ABCA4 (c.4926C>G and c.5044_5058del) and USH2A (c.2276G>T). All variants were present homozygously in DNA from the proband and heterozygously in DNA from the father. No variants were found in maternal DNA. Further analysis of single nucleotide polymorphisms confirmed paternal UPD of chromosome 1. This is the first known patient with confirmed UPD for two recessively mutated IRD genes. Our study expands on the genetic heterogeneity of IRDs and highlights the importance of UPD as a mechanism of autosomal recessive disease in non-consanguineous parents. Moreover, a long-term follow-up is essential for the identification of retinal features that may develop as a result of USH2A-related conditions.

Familial exudative vitreoretinopathy: A report of an asymptomatic case with autosomal dominant inheritance detected using FZD4 molecular analysis. / Vitreorretinopatía exudativa familiar, reporte de un caso asintomático con herencia autosómica dominante, detectado mediante análisis molecular de FZD4.

OBJECTIVE: To report a familial case of Familial Exudative Vitreoretinopathy (FEVR) with an autosomal dominant inheritance pattern identified with the molecular analysis of FZD4. CASE REPORT: The proband is a 13 year-old boy who consulted for low vision. Fundus examination revealed a peripheral avascular zone and macular dragging, consistent with FEVR. Molecular analysis demonstrated a mutation of FZD4 in DNA from both the patient and his asymptomatic mother. DISCUSSION: This familial case was identified with the molecular analysis of FZD4 and shows the importance to explore first degree relatives in a sporadic FEVR case.

Clinical, imaging, and molecular findings in a sample of Mexican families with pantothenate kinase-associated neurodegeneration.

Pantothenate kinase-associated neurodegeneration (PKAN) is an autosomal recessive disorder characterized by iron accumulation in the brain, because of mutations in the PANK2 gene. Phenotypic and genotypic characteristics of 11 patients from five Mexican families with PKAN disease are reported. Sequencing of PANK2 confirmed the diagnosis. The 11 patients had dysarthria associated with dystonia and Parkinsonism in six. Brain magnetic resonance imaging (MRI) showed the 'eye-of-the-tiger' sign in all patients. Three different mutations were identified, a novel one (p.A469P) and two (p.G219V and p.N404I) very rare. Homozygous sibs for the p.G219V mutation had a severe disease progression with early death. Dystonia predominated in the p.A469P/p.N404I compound heterozygous patients. Homozygous for p.N404I showed Parkinsonism, tics and personality and speech disorders. Early and late disease onset and variable expression was present in carriers of the different identified mutations. The 'eye-of-the-tiger' is an excellent neuroimaging hallmark to predict PANK2 mutations. We detected a 'cluster' of patients harboring the p.N404I mutation, strongly suggesting a founder effect for this mutation. This is the first familial clinical-genetic PKAN disease study accomplished in Mexico.

Macular optical coherence tomography findings and GPR143 mutations in patients with ocular albinism.

The aim of this study was to describe macular findings using spectral-domain optical coherence tomography (SD-OCT) in patients with ocular albinism (OA) and their carrier mothers, and to identify the frequency of GPR143 gene mutations in these patients. The study included five patients with a clinical diagnosis of OA. SD-OCT of the macular area was performed in both patients and their mothers. The anatomical characteristics of the macula and retinal pigment epithelium (RPE), patterns of autofluorescence and infrared imaging were analyzed. Polymerase chain reaction amplification of the complete coding sequence of GPR 143 was performed and subsequently analyzed by direct sequencing in patients and their possible carrier mothers. SD-OCT images revealed the presence of inner retinal layers in the fovea, an abnormal disposition of the Henle layer and a lack of thickening in the perifoveal area. We found increased thickness in the RPE to the outer segment and in the outer segment to the outer nuclear layer that is associated with increased visual acuity. Autofluorescence images revealed an absence of normal hipoautofluorescence in the fovea. No changes were observed in the images of their carrier mothers. Mutation screening and sequence analysis of the GPR 143 gene revealed a novel pathological mutation in two patients. Abnormalities in the macula were observed in all patients. SD-OCT is a useful tool for the assessment of patients with OA. No changes were observed in the SD-OCT of carrier mothers. Only two patients had the GPR143 gene mutation.

A novel gene mutation in PANK2 in a patient with an atypical form of pantothenate kinase-associated neurodegeneration.

Pantothenate kinase-associated neurodegeneration (PKAN) disease is an autosomal recessive neurodegenerative disorder with iron storage in the brain due to PANK2 gene mutations. Brain magnetic resonance imaging (MRI) shows the typical "eye-of-the-tiger" sign. The aim of the present study was to describe clinical, MRI and molecular findings in a 26-year-old male with atypical PKAN disease in whom, brain MRI scans showed bilateral pallidal T2-hypointensity with a small central region of T2-hyperintensity, resembling the "eye-of-the-tiger" typical image. Genetic analysis identified two mutations in PANK2: c.1561G>A and c.1663G>A, being the latter never described before. Due to limited phenotype-genotype correlation among patients with movement disorders, if "eye-of-the-tiger" brain MRI is present, PANK2 mutations investigation are needed to confirm PKAN disease.

A Novel De Novo EFNB1 Gene Mutation in a Mexican Patient with Craniofrontonasal Syndrome.

Craniofrontonasal syndrome (CNFS) is an X-linked disorder caused by mutations in the EFNB1 gene in which, paradoxically, heterozygous females are more severely affected than hemizygous males. In this paper, the clinical and molecular studies of a female subject with CFNS are described. A novel de novo c.473T>C (p.M158T) mutation in exon 3 of EFNB1 was demonstrated in this patient. The M158 residue of the Ephrin-B1 protein is highly conserved between species. Our results expand the mutational spectrum exposed by CNFS.

Immunophenotyping in peripheral blood mononuclear cells, aqueous humour and vitreous in a Blau syndrome patient caused by a novel NOD2 mutation.

The genetic and immunophenotypic characteristics of a 3-year-old patient with Blau syndrome (BS), an early onset sarcoidosis caused by mutations in NOD2, were investigated. Molecular analysis of NOD2 gene was achieved by PCR and direct nucleotide sequencing. Immunophenotyping included cytometric analysis of memory-effector markers on T-cells, and cytokine in serum, aqueous humour and vitreous. A novel M513R mutation in NOD2 was demonstrated. Immunophenotyping revealed higher frequency of CCR4+ cells and CCR9+ cells on CD4+ cells; most CD8+ cells were CCR7- and CCR9+. IL6 and IL-8 were detected in a gradient manner: vitreous humour>aqueous humour>serum. The immunophenotype in this patient was characterized by a differential expression of chemokine receptors on T cells and by a particular ocular microenvironment enriched in IL-6 and IL-8. To our knowledge, this is the first study analysing the immunological features of BS at aqueous humour, vitreous and blood levels. Our results expand the knowledge of the genetic and immunopathological basis of BS.

Novel sonic hedgehog mutation in a couple with variable expression of holoprosencephaly.

Holoprosencephaly (HPE) is the most common developmental defect of the forebrain and midface in humans. sporadic and inherited mutations in the human sonic hedgehog (SHH) gene cause 37% of familial HPE. A couple was referred to our unit with a family history of two spontaneous first trimester miscarriages and a daughter with HPE who presented early neonatal death. The father had a repaired median cleft lip, absence of central incisors, facial medial hypoplasia, and cleft palate. Intelligence and a brain CT scan were normal. Direct paternal sequencing analysis showed a novel nonsense mutation (W127X). Facial characteristics are considered as HPE microforms, and the pedigree suggested autosomal dominant inheritance with a variable expression of the phenotype. This study reinforces the importance of an exhaustive evaluation of couples with a history of miscarriages and neonatal deaths with structural defects.

Mutational screening of CHX10, GDF6, OTX2, RAX and SOX2 genes in 50 unrelated microphthalmia-anophthalmia-coloboma (MAC) spectrum cases.

BACKGROUND/AIMS: Microphthalmia-anophthalmia-coloboma (MAC) are congenital eye malformations causing a significant percentage of visually impairments in children. Although these anomalies can arise from prenatal exposure to teratogens, mutations in well-defined genes originate potentially heritable forms of MAC. Mutations in genes such as CHX10, GDF6, RAX, SOX2 and OTX2, among others, have been recognised in dominant or recessive MAC. SOX2 and OTX2 are the two most commonly mutated genes in monogenic MAC. However, as more numerous samples of MAC subjects would be analysed, a better estimation of the actual involvement of specific MAC-genes could be made. Here, a comprehensive mutational analysis of the CHX10, GDF6, RAX, SOX2 and OTX2 genes was performed in 50 MAC subjects. METHODS: PCR amplification and direct automated DNA sequencing of all five genes in 50 unrelated subjects. RESULTS: Eight mutations (16% prevalence) were recognised, including four GDF6 mutations (one novel), two novel RAX mutations, one novel OTX2 mutation and one SOX2 mutation. Anophthalmia and nanophthalmia, not previously associated with GDF6 mutations, were observed in two subjects carrying defects in this gene, expanding the spectrum of GDF6-linked ocular anomalies. CONCLUSION: Our study underscores the importance of genotyping large groups of patients from distinct ethnic origins for improving the estimation of the global involvement of particular MAC-causing genes.

Mutations in rpoB and katG genes in Mycobacterium isolates from the Southeast of Mexico.

The most frequent mutations associated with rifampin and isoniazid resistance in Mycobacterium are the substitutions at codons 531 and 315 in the rpoB and katG genes, respectively. Hence, the aim of this study was to characterize these mutations in Mycobacterium isolates from patients suspected to be infected with drug-resistant (DR) pulmonary tuberculosis (TB) in Veracruz, Mexico. Drug susceptibility testing of 25 clinical isolates revealed that five were susceptible while 20 (80%) were DR (15% of the annual prevalence for Veracruz). Of the DR isolates, 15 (75%) were resistant to rifampin, 17 (85%) to isoniazid and 15 (75%) were resistant to both drugs (MDR). Sequencing analysis performed in the isolates showed that 14 (93%) had mutations in the rpoB gene; seven of these (47%) exhibited a mutation at 531 (S-->L). Ten (58%) of the 20 resistant isolates showed mutations in katG; nine (52%) of these 10 exhibited a mutation at 315 (S-->T). In conclusion, the DR profile of the isolates suggests a significant number of different DR-TB strains with a low frequency of mutation at codons 531 and 315 in rpoB and katG, respectively. This result leads us to consider different regions of the same genes, as well as other genes for further analysis, which is important if a genetic-based diagnosis of DR-TB is to be developed for this region.

Mutations in rpoB and katG genes in Mycobacterium isolates from the Southeast of Mexico

The most frequent mutations associated with rifampin and isoniazid resistance in Mycobacterium are the substitutions at codons 531 and 315 in the rpoB and katG genes, respectively. Hence, the aim of this study was to characterize these mutations in Mycobacterium isolates from patients suspected to be infected with drug-resistant (DR) pulmonary tuberculosis (TB) in Veracruz, Mexico. Drug susceptibility testing of 25 clinical isolates revealed that five were susceptible while 20 (80 percent) were DR (15 percent of the annual prevalence for Veracruz). Of the DR isolates, 15 (75 percent) were resistant to rifampin, 17 (85 percent) to isoniazid and 15 (75 percent) were resistant to both drugs (MDR). Sequencing analysis performed in the isolates showed that 14 (93 percent) had mutations in the rpoB gene; seven of these (47 percent) exhibited a mutation at 531 (S[L). Ten (58 percent) of the 20 resistant isolates showed mutations in katG; nine (52 percent) of these 10 exhibited a mutation at 315 (S[T). In conclusion, the DR profile of the isolates suggests a significant number of different DR-TB strains with a low frequency of mutation at codons 531 and 315 in rpoB and katG, respectively. This result leads us to consider different regions of the same genes, as well as other genes for further analysis, which is important if a genetic-based diagnosis of DR-TB is to be developed for this region.

Two different PABPN1 expanded alleles in a Mexican population with oculopharyngeal muscular dystrophy arising from independent founder effects.

BACKGROUND: Oculopharyngeal muscular dystrophy (OPMD) is a late onset hereditary myopathy of autosomal dominant transmission characterised by ptosis, dysphagia and limb weakness. The disease is caused by short heterozygous expansions of a (GCN)(10) triplet located in the first exon of the PABPN1 gene at chromosome 14q11.1. Most affected individuals from North America and Europe carry a mutant (GCN)(13) allele. Although evidence for a founder mutation effect has been shown in several populations with OPMD, analysis of large groups of patients from different ethnic backgrounds will help to identify the relative contribution of each allele to the disease and a possible genotype-phenotype correlation. METHODS: 22 unrelated patients with OPMD from Mexico, a previously uncharacterised population, were clinically and molecularly analysed. Detailed ophthalmological and clinical examinations were performed in each proband and molecular analysis of the PABPN1 gene was carried out by PCR amplification and allele-specific cloning/sequencing. Two single nucleotide polymorphisms (SNPs) linked to PABPN1 were determined in each individual and in a number of affected first-degree relatives. RESULTS: 15 subjects (68%) carried a mutant (GCN)(15) or (GCG)(11)(GCA)(3)(GCG) PABPN1 allele; the remaining 7 (32%) exhibited an abnormal (GCN)(13) or (GCG)(9)(GCA)(3)(GCG) allele. Analysis of two SNPs linked to PABPN1 strongly suggests that both expanded alleles originate from two independent founder effects. In addition, in this particular population the (GCN)(15) allele was associated with an earlier onset of the disease (mean 46.5 years) compared with the (GCN)(13) allele (mean 54.7 years). CONCLUSION: The results of this study suggest that OPMD in the Mexican population is mostly due to (GCG)(11) or (GCG)(9) PABPN1 expanded alleles arising from two independent founder effect mutations. These findings add to the definition of the genetic features of the disease and to the establishment of a probable genotype-phenotype correlation.

[PCR-based detection of heteroplasmic deleted mitochondrial DNA in Kearns-Sayre syndrome]. / Detección de deleciones en DNA mitocondrial heteroplásmico por medio de PCR EN el síndrome de Kearns-Sayre.

OBJECTIVE: To describe the clinical data and the results of molecular analyses of the mitochondrial DNA in a patient with Kearns-Sayre Syndrome. METHODS: Molecular analyses of mitochondrial DNA from the patient included PCR amplification of a region where the common Kearns- Sayre deletion is located and Genotype-Phenotype correlations are discussed. RESULTS: The affected patient showed ptosis, progressive external ophthalmoplegia, pigmentary changes in the peripheral retina and right bundle block. Molecular analysis disclosed a approximately 5 kb deletion in the mitochondrial DNA and some wild type mtDNA indicating heteroplasmy. CONCLUSIONS: Molecular analysis of mitochondrial DNA confirmed the clinical diagnosis of Kearns-Sayre syndrome. PCR provides a rapid method to identify the common 4997 bp deletion in Kearns-Sayre syndrome. In such cases, PCR diagnosis could avoid invasive methods such as muscle biopsy or spinal tap.

[Autosomal dominant granular corneal dystrophy caused by a TGFBI gene mutation in a Mexican family]. / Distrofia corneal granular autosómica dominante causada por mutación del gen TGFBI en una familia Mexicana.

OBJECTIVE: To describe the clinical data and the results of molecular analyses of the TGFBI gene in a patient with classic granular stromal corneal dystrophy (type I). METHODS: A female patient aged 60-years complaining of a long-standing decrease of visual acuity bilaterally associated with photophobia and foreign body sensation, underwent a complete ophthalmologic examination. Molecular analyses of DNA from the patient and from an affected brother included PCR amplification of exons 4, 11, 12, and 14 of the TGFBI gene and direct automated sequencing of the PCR products. RESULTS: The affected patient showed a pattern of corneal stromal lesions that was compatible with a diagnosis of classic granular dystrophy. No involvement of other corneal layers was evident. Molecular analysis disclosed a point mutation in exon 14 of the TGFBI gene which consisted of an adenine to guanine change at nucleotide position 1924, predicting a substitution of arginine instead of histidine at residue 626 of the TGFBI protein (H626R). An identical mutation was detected in DNA from her affected brother. CONCLUSIONS: This is the first time that a case of stromal granular dystrophy has been demonstrated to be caused by the H626R mutation, a molecular defect classically detected in the phenotypically distinct lattice corneal dystrophy. Our data indicate that the same molecular defects in the TGFBI gene lead to different phenotypes in stromal dystrophies, thus expanding the genotypic-phenotypic spectrum in this group of corneal diseases.

Clinical and cytogenetic findings in 14 patients with madelung anomaly.

Madelung deformity of the wrist is a congenital defect caused by a growth disturbance in the volar-ulnar distal radial physis leading to a typical appearance of the upper extremities. The majority of Madelung deformity case caused by hereditary dyschondrosteosis of the wrist. In a number of instances, the disease has a genetic etiology. This article reports the clinical and cytogenetic findings associated with Madelung deformity in 14 patients. Results indicate Madelung anomaly often is associated with additional clinical abnormalities, particularly delayed puberty and menstrual disorders, as well as sexual chromosome aberrations.

p63 gene analysis in Mexican patients with syndromic and non-syndromic ectrodactyly.

Ectrodactyly is a congenital limb malformation that involves a central reduction defect of the hands and/or feet which is frequently associated with other phenotypic abnormalities. The condition appears to be genetically heterogeneous and recently it has been demonstrated that mutations in the p63 gene, a homologue of the tumor suppressor gene p53, are the cause of at least four autosomal dominant genetic syndromes which feature ectrodactyly: ectrodactyly, ectodermal dysplasia, and facial clefting (EEC), split hand/split foot malformation (SHFM), limb-mammary syndrome (LMS), and acro-dermato-ungual-lacrimal-tooth syndrome (ADULT). In this study, genetic analysis of the p63 gene in a group of 13 patients with ectrodactyly (syndromic and isolated) was performed. Four patients with syndromic ectrodactyly had p63 heterozygous point mutations that affect the DNA binding domain of the protein. One of these subjects exhibited the typical features of EEC syndrome as well as ankyloblepharon being, to our knowledge, the first case combining these traits. This finding supports the view of a clinical overlap in this group of autosomal dominant syndromes caused by p63 mutations and demonstrates that there are exceptions in the previously established p63 genotype-phenotype correlation.

A de novo phe671eu mutation in the SRY gene in a patient with complete 46,XY gonadal dysgenesis.

The sex-determining region of the Y chromosome (SRY) gene initiates the process of male sex differentiation in mammalians. In humans, mutations in the SRY gene have been reported to account for 10-15% of the XY sex reversal cases. In this report we describe the clinical, endocrinological and molecular data of a patient with complete 46,XY gonadal dysgenesis caused by a de novo mutation affecting SRY amino acid phenylalanine at position 67 (F67L), located within the highly conserved high mobility group (HMG) box coding region of the gene.