Genetic analysis of TMPRSS6 catalytic domain variants in Mexican patients with iron treatment refractoriness.

OBJECTIVE: To identify the TMPRSS6 gene variants in Mexican patients with iron treatment refractoriness, to describe hematological and iron profile parameters, and to use bioinformatic prediction and protein modeling tools to assess a possible biological impact for the detected missense variants. METHODS: Nineteen patients referred with iron treatment refractoriness were studied. Peripheral blood was collected to determine hematic cytometry, iron profile, hemoglobin electrophoresis, and quantification. Molecular screening was carried out for exons 15 through 18 of the TMPRSS6 gene by Sanger sequencing and for frequent thalassemia variants by amplification-refractory mutation system-polymerase chain reaction (PCR) and gap-PCR. The biological impact of the detected missense variants was assessed using bioinformatic prediction and protein modeling tools. RESULTS: We found 5 genetic variants in the matriptase-2 catalytic domain: 1 at intron-15/exon-16 junction (rs60484081) and 4 exonic, 3 missense (rs377054987, p.Gly626Asp; rs1384127820, p.Ser672Thr; rs855791, p.Val727Ala) and 1 synonymous (rs2235321, p.Tyr730=), with frequencies ranging from 0.18 to 0.53. No significant differences were observed in the hematological parameters or iron profile, considering type and number of variants. Bioinformatic predictions suggested a possible biological impact only for rs377054987. CONCLUSIONS: The TMPRSS6 variants observed in Mexican patients with oral iron treatment refractoriness have high frequencies; nevertheless, their relationship with hematological and iron profile parameters needs further research. The possible biological impact for rs377054987 is due to size and amino acid hydrophobicity changes and hydrogen bond modifications.

Effects of SPTA1 Gene Variants on the Hematological Phenotype of Mexican Patients with Hereditary Spherocytosis.

Introduction: Hereditary spherocytosis (HS) is a common hereditary hemolytic anemia characterized by chronic hemolysis, increased indirect serum bilirubin, the presence of reticulocytes and spherocytes in blood smears, and great heterogeneity at the clinical, biochemical, and molecular levels. The molecular pathology of HS includes genetic variants at five genes: ANK1, EPB42, SLC4A1, SPTA1, and SPTB. Alpha spectrin (SPTA1) deficiency is the second leading cause of HS in Mexican patients. Aim: To assess the effects of five SPTA1 variants on the hematological phenotype of Mexican patients with HS. Materials and Methods: This study included a retrospective cohort of 227 biologically unrelated patients with HS. Variants c.4339-99C>T and c.6531-12C>T in SPTA1 were identified by the amplification-refractory mutation system polymerase chain reaction (ARMS-PCR), and variants c.5572C>T, c.5992C>G, and c.6794T>C were identified by quantitive Real Time-Polymerase Chain Reaction (qRT-PCR) allelic discrimination. Risk tests were performed for each variant with respect to HS clinical severity. Results: The SPTA1 c.5992C>G variant showed association with moderately severe HS (p = 0.006, odds ratio = 5.67, confidence interval95% = 1.6-19.9); the risk increased when the variant was in compound heterozygosity with αLELY and c.6794T>C. Lower hematological levels were observed in simple αLely (c.5572C>T and c.6531-12C>T), and c.5992C>G heterozygotes (red blood cell [RBC] p = 0.028 and 0.010; hemoglobin [Hb] p = 0.030 and 0.002; packed cell volume [PCV] p = 0.034 and 0.002 respectively), and in c.5992C>G+c.6794T>C compound heterozygotes (RBC p = 0.043; Hb p = 0.033; PCV p = 0.043). Additional genetic traits were observed: 15% had HS+Gilbert syndrome and 13% HS+thalassemia. Conclusion: Although most of the studied variants are considered benign, we observed significant associations with phenotypic severity. Therefore, we recommend the inclusion of these variants in molecular screening for HS.

Hematological and molecular analysis of patients with G6PD deficiency revealed coexistent hereditary spherocytosis and alpha thalassemia.

BACKGROUND: Glucose-6-phosphate dehydrogenase (G6PD) deficiency, hereditary spherocytosis (HS), and alpha thalassemia (α-thal) are frequent erythrocyte pathologies with different geographic distributions worldwide. Our aim is to report hematological and molecular findings of G6PD deficient Mexican patients in coinheritance with suggestive hereditary spherocytosis (sHS) and α-thal. METHODS: We studied 78 G6PD deficiency patients. Hematological parameters, acidified glycerol lysis test, erythrocyte morphology, electrophoresis, and hemoglobin quantification were obtained. G6PD and HBA2/HBA1 variants were identified using ARMS-PCR, Gap-PCR, or Sanger sequencing. RESULTS: Nine G6PD variants were identified; A-202A/376G , A-376G/968C , and A+376G as the most frequent. G6PD Santiago de Cuba1339A and Kamiube1387T were detected in Mexicans for first time. Hematological analysis revealed additional erythrocyte pathologies in 52 patients, 32 with positive osmotic fragility test and spherocytes in blood smear (suggestive hereditary spherocytosis, sHS), 12 with microcytosis and 8 with all three defects who had the most severe phenotype, with significantly lower hematological parameters (Hb, PCV, MCV, and MCH). α-thal variants (αHph α, α-59C>T α and -α3.7 ) were observed in 65% of patients with microcytosis. CONCLUSION: Additional erythrocyte defects were observed in 69.3% of G6PD deficiency patients. We stress the importance of searching for the presence of additional erythrocyte hereditary diseases in patients with G6PD deficiency.

Molecular and Hematological Analysis of Alpha- and Beta-Thalassemia in a Cohort of Mexican Patients.

Introduction: Alpha- and beta-thalassemia are caused by reduced or absent synthesis of hemoglobin (Hb) subunits α and/or ß. HBA2, HBA1, and HBB mutations are the main cause of thalassemias. The aim of this article is to analyze molecular and hematological features of α- and ß-thal in a cohort of Mexican patients. Methods: One hundred forty-one thalassemia patients were studied. Peripheral blood was collected for blood cell count, electrophoresis, Hb quantification, and molecular testing. Molecular screening was performed by Gap-PCR, ARMS-PCR, Sanger sequencing, and MLPA. Results: Fifty-four patients had α-thal, 75 ß-thal, and 12 patients were complex cases, we observed 13 α- and 18 ß-thal alleles in 43 genotypes, -α3.7/αα and ßCd39C>T/ß were the most frequent. Four α-thal deletions (-Mex4 included HBA2 and HBA1, whereas (αα)Mex5, Mex6 and Mex7 involved MCS-R), a hereditary persistence of fetal hemoglobin-2 like (HPFH-2 like) deletion and six alleles not previously reported in Mexicans (α-59C>Tα, -α4.2, αPlasenciaα, ß-32C>T, ßInitCdA>C and ßFSCd71/72+A) were identified. Conclusion: The observed alleles denote the high heterogeneity and multiple origin admixture of Mexican population. Hematological data are consistent with genotypes, variability in simple carriers, from asymptomatic forms to mild or moderate anemia, was ascertained. We emphasize the importance to consider hematological parameters to establish adequate molecular screening strategies.

Hemoglobina Fannin-Lubbock I y II, dos variantes que comparten una mutación / Hemoglobin Fannin-Lubbock I and II, two variants sharing a mutation

Hemoglobin (Hb) Fannin-Lubbock I (beta119 [GH2]), GGC>GAC, Gly>Asp) and Hb Fannin-Lubbock II (beta111 [G13]), GTC>CTC, Val>Leu and beta 119 (GH2), GGC >GAC, Gly>Asp), share the mutation at position 119, both abnormal hemoglobins have similar fast electrophoretic mobility due the Gly>Asp change. Hb Fannin-Lubbock, is classified in the group of unstable hemoglobins, without alteration in their affinity for oxygen; the mutation at amino acid 119 and that of amino acid 111 participate in the interaction of the alpha1beta1 chains, with important links in the stability of the molecule, so that both substitutions could affect the stability of the molecule. Initially the instability of the variant was attributed to mutation 111, however, our group confirmed that the mutation at amino acid 119 is responsible for the instability to the molecule. In this paper, we analyze the first observations of Hb Fannin-Lubbock in 1976 and in 1982, the demonstration of Hb Fannin-Lubbock II by DNA sequencing as well as the evidence of two different mutations by DNA analysis, the Hb Fannin-Lubbock I observed mainly in families of Mexican origin and Hb Fannin-Lubbock II in families of Spanish origin, we also present the hematological characteristics of both types and the indirect evidence that the Hb Fannin-Lubbock I observed in a Mexican family and in a Hind

La hemoglobina (Hb) Fannin-Lubbock I (beta119 (GH2), GGC>GAC, Gly>Asp) y la Hb Fannin-Lubbock II (beta111 (G13), GTC>CTC, Val>Leu y beta119 (GH2), GGC>GAC, Gly>Asp), comparten la mutación en la posición 119, tienen movilidad electroforética rápida similar debida al cambio Gly>Asp. La Hb FanninLubbock se clasifica en el grupo de hemoglobinas inestables, sin alteración en su afinidad por el oxígeno; tanto la mutación en el aminoácido 119 como la del aminoácido 111 participan en la interacción de las cadenas alfa1beta1, por lo que ambas sustituciones podrían afectar la estabilidad de la molécula. Inicialmente la inestabilidad de la Hb se atribuyó a la mutación 111, sin embargo, nuestro grupo confirmó que la mutación en el aminoácido 119 es la responsable de la inestabilidad de la molécula. En este trabajo se analizan las primeras observaciones de la Hb Fannin-Lubbock en 1977 y en 1982, la demostración de la Hb Fannin-Lubbock II por secuenciación de ADN, así como la evidencia de dos mutaciones diferentes por análisis de ADN, la Hb Fannin-Lubbock I observada principalmente en familias de origen mexicano y la Hb Fannin-Lubbock II en familias de origen español, así como las características hematológicas de ambos tipos y la evidencia indirecta de que la Hb Fannin-Lubbock I observada en una familia mexicana y en una familia india se asocian con haplotipos beta distintos, lo que sugiere que surgieron por eventos mutacionales independientes

[Polymorphism analysis of G199A, Ncol in ANK1 and Memphis I in SLC4A1 genes in Mexican healthy individuals and subjects affected with hereditary spherocytosis]. / Andálisis de los polimorfismos G199A, NcoI del gen ANK1 y Memphis I del gen SLC4A1 en individuos sanos y pacientes mexicanos con esferocitosis hereditaria.

BACKGROUND: In Mexico, Hereditary Spherocytosis (HS) is the main cause of hereditary hemolytic anemia, due to mutations of one or more genes involved in the erythrocyte membrane, making it difficult to identify the primary gene. OBJECTIVE: With the purpose of estimating the use of the polymorphisms G199A and NcoI of ANK1 gene, and Memphis I of SLC4A1 gene, as genetic markers to screen this disease, we searched the allelic and genotypic frequencies in 45 DNA samples of HS patients and 28 from healthy individuals. RESULTS: Allelic and genotypic frequencies were similar in both studied groups for the G199A and Memphis I polymorphisms, with low frequency of heterozygosis showing its limited use as a genetic marker. The allelic and genotypic frequencies of the NcoI polymorphism were also similar in both groups, however a higher heterozygote frequency was observed (0.49 and 0.43 in patients and healthy individuals), a feature that may turn it into a useful genetic marker. CONCLUSIONS: Since there are other genes implicated in the molecular pathology of the HS, we consider it necessary to continue analyzing other polymorphisms of the genes involved in Hereditary Spherocytosis among the Mexican population.

Andálisis de los polimorfismos G199A, NcoI del gen ANK1 y Memphis I del gen SLC4A1 en individuos sanos y pacientes mexicanos con esferocitosis hereditaria / Polymorphism analysis of G199A, Ncol in ANK1 and Memphis I in SLC4A1 genes in Mexican healthy individuals and subjects affected with hereditary spherocytosis

Antecedentes. En México la esferocitosis hereditaria (EH) es la causa principal de anemia hemolítica hereditaria y se debe a mutaciones en uno o más genes implicados en la membrana eritrocitaria, lo que dificulta la identificación del gen primario. Objetivo. Con el fin de valorar la utilización de los polimorfismos G199A y NcoI del gen ANK1, y Memphis I del gen SLC4A1 como marcadores genéticos para identificar esta enfermedad, estimamos sus frecuencias alélicas y genotípicas en 45 muestras de ADN de pacientes con EH y 28 de individuos sanos, las cuales fueron similares en uno y otro grupos para los polimorfismos G199A y Memphis I, con baja frecuencia de heterocigotos, lo que limita su utilidad como marcador genético. Resultados. El polimorfismo NcoI no mostró diferencias alélicas y genotípicas en los grupos de estudio, pero sí mayor frecuencia de heterocigotos (0.49 y 0.43 en enfermos y sanos respectivamente), característica que le confiere ventajas para ser utilizado como marcador genético en familias con EH. Conclusiones. Finalmente, debido a que existen otros genes implicados en la patología molecular de la EH, consideramos que es necesario analizar otros polimorfismos de genes que codifican para las proteínas involucradas en las deficiencias que conducen a esferocitosis hereditaria en la población mexicana.

BACKGROUND: In Mexico, Hereditary Spherocytosis (HS) is the main cause of hereditary hemolytic anemia, due to mutations of one or more genes involved in the erythrocyte membrane, making it difficult to identify the primary gene. OBJECTIVE: With the purpose of estimating the use of the polymorphisms G199A and NcoI of ANK1 gene, and Memphis I of SLC4A1 gene, as genetic markers to screen this disease, we searched the allelic and genotypic frequencies in 45 DNA samples of HS patients and 28 from healthy individuals. RESULTS: Allelic and genotypic frequencies were similar in both studied groups for the G199A and Memphis I polymorphisms, with low frequency of heterozygosis showing its limited use as a genetic marker. The allelic and genotypic frequencies of the NcoI polymorphism were also similar in both groups, however a higher heterozygote frequency was observed (0.49 and 0.43 in patients and healthy individuals), a feature that may turn it into a useful genetic marker. CONCLUSIONS: Since there are other genes implicated in the molecular pathology of the HS, we consider it necessary to continue analyzing other polymorphisms of the genes involved in Hereditary Spherocytosis among the Mexican population.