Harvy Velasco

SHOX gene and conserved noncoding element deletions/duplications in Colombian patients with idiopathic short stature

SHOX gene mutations or haploinsufficiency cause a wide range of phenotypes such as Leri Weill dyschondrosteosis (LWD), Turner syndrome, and disproportionate short stature (DSS). However, this gene has also been found to be mutated in cases of idiopathic short stature (ISS) with a 3–15% frequency. In this study, the multiplex ligation‐dependent probe amplification (MLPA) technique was employed to determine the frequency of SHOX gene mutations and their conserved noncoding elements (CNE) in Colombian patients with ISS. Patients were referred from different centers around the county. From a sample of 62 patients, 8.1% deletions and insertions in the intragenic regions and in the CNE were found. This result is similar to others published in other countries. Moreover, an isolated case of CNE 9 duplication and a new intron 6b deletion in another patient, associated with ISS, are described. This is one of the first studies of a Latin American population in which deletions/duplications of the SHOX gene and its CNE are examined in patients with ISS.

Deep Genotyping of the IDS Gene in Colombian Patients with Hunter Syndrome

BACKGROUND Mucopolysaccharidosis type II (MPSII), also known as Hunter syndrome, is an X-linked disorder caused by mutations in the iduronate 2 sulfatase (IDS) gene. This enzyme catalyzes the initial step in the catabolism of heparan sulfate and dermatan sulfate; thus, its deficiency leads to the accumulation of these glycosaminoglycans. MPS II has significant allelic heterogeneity, making the establishment of genotype-phenotype correlations difficult. This study assessed clinical features in combination with deep genotyping of a group of Colombian patients with MPS II and attempted to establish a degree of genotype-phenotype correlation by employing bioinformatic tools. METHODS Eighteen patients were included in this study, 11% of whom were non-neuronopathic, and the other 89% were neuronopathic. Samples were all analyzed using three molecular methodologies: MLPA, direct exon sequencing, and RFLP analysis. RESULTS A total of 13 mutations were identified, 6 of which were novel (c.548_564dup16, c.477insT, c.595_607del12, c. 549_562del13, c.182delC, and a complete deletion of exon 7). The frequency of common mutations (R468Q, Q465X, K347Q, K236N, S71N, R88H, and a conversion phenomenon) was 53.85%. The S71N mutation was frequent among the attenuated phenotype, while private frameshift mutations and rearrangements were seen in patients with severe phenotypes. Molecular docking was performed on the wild-type and mutant IDS proteins, which revealed changes in the enzyme-substrate interaction for the mutant IDS. CONCLUSION The frequency of novel mutations (46.15%) is similar to what has been reported elsewhere. The use of bioinformatic tools showed differences in enzyme-substrate interactions. Studies with larger groups of patients are needed.

Natural History of Sanfilippo Syndrome Type C in Boyacá, Colombia: A Neurogenetic Description

Mucopolysaccharidosis type III, or Sanfilippo syndrome, is an autosomal recessive disorder characterized by impairment in the degradation of Heparan sulfate. Here the authors describe the natural history of 5 related individuals; all associated through a large pedigree which reports a total of 11 affected members, originally from the Boyacá region in Colombia, diagnosed with MPS IIIC who all harbor a novel mutation in HGSNAT. The authors report an unusually high incidence of the disease in this population. The clinical features are similar to previously described patients, although some differences in the degree of severity and end-stage of the disease are seen in this specific group. The authors consider that the high degree of endogamy in this specific population could underlie modifying factors for the severity of presentation in these patients. Future studies might provide more information on the functional effect of this novel mutation, which could define this group as a genetic isolate.

Genotypic and bioinformatic evaluation of the alpha-L-iduronidase gene and protein in patients with mucopolysaccharidosis type I from Colombia, Ecuador and Peru

Mucopolysaccharidosis type I (MPSI) is a rare autosomal recessive disorder caused by mutations in the gene encoding the lysosomal enzyme α-l-iduronidase (IDUA), which is instrumental in the hydrolysis of the glycosaminoglycans, dermatan and heparan sulfate. The accumulation of unhydrolyzed glycosaminoglycans leads to pathogenesis in multiple tissue types, especially those of skeletal, nervous, respiratory, cardiovascular, and gastrointestinal origin. Although molecular diagnostic tools for MPSI have been available since the identification and characterization of the IDUA gene in 1992, Colombia, Ecuador, and Peru have lacked such methodologies. Therefore, the mutational profile of the IDUA gene in these countries has largely been unknown. The goal of this study was to characterize genotypes in 14 patients with MPSI from Colombia, Ecuador, and Peru. The most common mutation found at a frequency of 42.8% was W402X. Six patients presented with seven novel mutations, a high novel mutational rate in this population (32%). These novel mutations were validated using bioinformatic techniques. A model of the IDUA protein resulting from three of the novel missense mutations (Y625C, P385L, R621L) revealed that these mutations alter accessible surface area values, thereby reducing the accessibility of the enzyme to its substrates. This is the first characterization of the mutational profile of the IDUA gene in patients with MPSI in Colombia, Ecuador, and Peru. The findings contribute to our understanding of IDUA gene expression and IDUA enzyme function, and may help facilitate early and improved diagnosis and management for patients with MPSI.

In silico Analysis of Iduronate 2 Sulfatase Mutations in Colombian Patients with Hunter Syndrome (MPSII)

Hunter syndrome or Mucopolysaccharidosis II is an inherited X linked disease, caused by mutations in iduronate 2 sulfatase (IDS), enzyme which catalyzes the initial step reaction of heparan and dermatan sulfate degradation. Allelic heterogeneity in MPSII challenges genotype-phenotype correlation. With the aim of understanding the repercussion of mutations on enzyme structure-function, we performed protein modeling and docking simulations with wild and mutant forms of hIDS. Mutations were obtained from a molecular study conducted in Colombian patients. Point mutations affected substrate-protein interactions. In the case of S71N (attenuated phenotype) further experimentation is required. Novel mutants P160SfsX4, D190Pfs13X and P185GfsX2 have a severely distorted conformation. Detailed analysis of the ligand-protein interaction is also of great significance in designing molecules for treatment. This is the first report of molecular docking performed with wild and mutant forms of iduronate-2-sulfatase as a bioinformatical approach to phenotype-genotype correlation in patients with Hunter Syndrome in Colombia.

Incidentalome in Neurogenetics: Pathogenic Variant of NSD1 in a Patient With Spinocerebellar Ataxia (SCA)

Background: Genetic studies of late-onset sporadic ataxias (>40 years of age) are not routinely indicated. For unresolved cases, next-generation sequencing (NGS) tools, such as whole-exome sequencing (WES), are available for a definitive diagnosis. Case presentation: Our patient is a woman with a usual facial phenotype and anthropometry, who developed ataxia at 45 years of age, with no relevant family history and an initial clinical approach that ruled out common aetiologies. WES was performed when the patient was 54 years old. The results identified the heterozygous pathogenic variant c.248delA (p.N83MfsX4) in the nuclear receptor-binding SET domain protein 1 (NSD1; MIM 606681) gene (related to Sotos syndrome), which was not associated with ataxia and is not related to the patients phenotype. Sanger sequencing of NSD1 in two different laboratories confirmed the variant. Conclusions: NGS findings generally offer valuable information that can be used for clinical decision-making. However, an incidental finding that leads to defining new clinical and bioethical actions is also possible. Consequently, the biological importance of this type of genetic “incidentalome” must be determined.

Genética clínica comunitaria: exploración de patología genética en Boyacá, Colombia

OBJECTIVES To explore the incidence of syndromic genetic pathologies in Boyacá, Colombia, through a community genetics approach. MATERIALS AND METHODS A group made up by different medical specialists (geneticists, a pediatric neurologist, and a biochemical geneticist) developed clinical campaigns, in which patients with clinical suspicion of genetic diseases were involved. Demographic, epidemiological and clinical data were collected, and frequency calculations were made based on the collected data. Several training workshops for health personnel were done in each center visited. RESULTS Two genetic clusters were found: mucopolysaccharidosis type III, and Ellis-Van Creveld Syndrome, both of them with higher incidences than those found in the literature. Also, a high frequency of autosomal recessive diseases was found, as well as microdeletion/microduplication syndromes. CONCLUSIONS Conventional mechanisms of medical attention must be established, in order to facilitate the access to an appropriate diagnosis and treatment. This work intended to provide support to patients, families and health care services personnel through the workshops and clinical campaigns, and to become a starting point to develop primary and secondary prevention processes.

Caracterización de pacientes con enfermedades genéticas del esqueleto en un centro colombiano de remisión

INTRODUCTION Short height in Colombia has an estimated prevalence of 10%. The 2009 Nosology and Classification of Skeletal Genetic Diseases described 456 clinical conditions using biochemical, molecular and radiological criteria for diagnosis. OBJECTIVE To analyze demographic, epidemiological and clinical variables in a group of patients with skeletal genetic diseases referred to the Instituto de Ortopedia Infantil Roosevelt. MATERIALS AND METHODS Patients referred between 2008 and 2014 were analyzed filtering 167 diagnoses of the International Classification of Diseases, 10th revision (ICD 10), related to skeletal genetic diseases. Demographic, epidemiological and clinical variables were explored using descriptive statistics. An intervention score was generated contemplating different combinations of treatments. An inferential statistical analysis using Students t test was performed on such variables. RESULTS The most frequent reason for consultation was suspicion of a genetic skeletal disorder. The types of treatments considered included support, surgical, pharmacological and orthotics, and it was established that genetic skeletal disorders were associated with higher intervention scores while tall and short height showed a lower score. CONCLUSIONS Most referred patients were classified with genetic bone diseases, short stature and other monogenic genetic diseases. Significant differences were found between the age at symptoms onset and the age of diagnosis. Diversity was found in the therapeutic approach among different groups of pathologies. Patients with tall and short height showed lower intervention scores, which may warn on the need to reassess the therapeutic requirements of these groups.

Characterization of patients with genetic diseases of the skeleton in a Colombian referral center

INTRODUCTION Short height in Colombia has an estimated prevalence of 10%. The 2009 Nosology and Classification of Skeletal Genetic Diseases described 456 clinical conditions using biochemical, molecular and radiological criteria for diagnosis. OBJECTIVE To analyze demographic, epidemiological and clinical variables in a group of patients with skeletal genetic diseases referred to the Instituto de Ortopedia Infantil Roosevelt. MATERIALS AND METHODS Patients referred between 2008 and 2014 were analyzed filtering 167 diagnoses of the International Classification of Diseases, 10th revision (ICD 10), related to skeletal genetic diseases. Demographic, epidemiological and clinical variables were explored using descriptive statistics. An intervention score was generated contemplating different combinations of treatments. An inferential statistical analysis using Students t test was performed on such variables. RESULTS The most frequent reason for consultation was suspicion of a genetic skeletal disorder. The types of treatments considered included support, surgical, pharmacological and orthotics, and it was established that genetic skeletal disorders were associated with higher intervention scores while tall and short height showed a lower score. CONCLUSIONS Most referred patients were classified with genetic bone diseases, short stature and other monogenic genetic diseases. Significant differences were found between the age at symptoms onset and the age of diagnosis. Diversity was found in the therapeutic approach among different groups of pathologies. Patients with tall and short height showed lower intervention scores, which may warn on the need to reassess the therapeutic requirements of these groups.