5α-Reductase type 2 deficiency in families from an isolated Andean population in Venezuela.

5α-Reductase type 2 deficiency causes a 46,XY disorder of sex development (DSD) characterized by ambiguous external genitalia, rudimentary prostate, and normal internal genitalia. The disease prevalence worldwide is low, but in a small and isolated village of the Venezuelan Andes, a higher incidence has been found. DNA analysis of the SRD5A2 gene was performed in three inbred affected individuals clinically diagnosed with DSD. The entire coding regions, the p.L89V polymorphism (rs523349) and five intragenic SNPs (rs2300702, rs2268797, rs2268796, rs4952220, rs12470196) used to construct haplotypes were analyzed by Sanger sequencing. To assess the probable ethnic origin of the mutation in this geographic isolate, a population structure analysis was performed. Homozygosis for the p.N193S mutation was found in all patients, with a mutation carrier frequency of 1:80 chromosomes (0.0125) in the geographic focus, suggesting a founder phenomenon. The results of the population structure analysis suggested a mutation origin closer to the Spanish populations, according to the clusters grouping. The genotype-phenotype correlation in the patients was not absolute, being hypospadias and cryptorchidism the main traits that differentiate affected individuals.

Most Martin-Bell syndrome (FMR1-related disorder) Venezuelan patients did not show CGG expansion but instead display genetic heterogeneity.

Martin-Bell syndrome is mainly caused by the expansion of CGG trinucleotide repeats (>200 CGG) in the first exon of the FMR1 gene, leading to hypermethylation of the promoter region and silencing of the FMR1 protein expression. These changes are responsible for a phenotype with varying degrees of mental retardation, a long face with large and protruding ears, macroorchidism and autistic behavior. There may also be, however, patients who exhibit typical features of the syndrome without any expansion in the FMR1 gene; thus, other mechanisms affecting the expression of the FMR1 gene were assessed in 25 out of 29 ascertained patients with the typical phenotype without full mutation. Promoter methylation status of FMR1, mutations in its sequence and copy number variations (CNVs) in genes associated with intellectual disability were investigated. In 25 independent male patients without expansion, the promoter region was unmethylated; one patient with a full mutation showed methylation mosaicism; and a female patient had 81.2% of CpG sites methylated and 18.8% hemimethylated. One heterozygous duplication in exon 6 of the PDCD6 gene (programmed cell death 6) and a heterozygous deletion in exon 5 of the CHL1 gene (cell adhesion molecule L1), respectively, were found in two independent patients.

Spinocerebellar ataxias in Venezuela: genetic epidemiology and their most likely ethnic descent.

Dominantly inherited ataxias (spinocerebellar ataxias, SCAs) are a genetically heterogeneous group of neurologic diseases characterized by progressive cerebellar and spinal tract degeneration with ataxia and other signs, common to all known subtypes. Several types are relatively frequent worldwide, but in several countries, one specific SCA may show a higher prevalence owing to founder phenomena. In Venezuela, genetic epidemiological features of SCAs have been assessed during the last 30 years; mutations in ATXN1 (SCA1), ATXN2 (SCA2), ATXN3 (SCA3), CACNA1A (SCA6), ATXN7 (SCA7), ATXN8 (SCA8), ATXN10 (SCA10), TBP (SCA17) and ATN1 (dentatorubral pallidoluysian atrophy, DRPLA) loci were searched among 115 independent families. SCA7 was the most frequent subtype (26.6%), followed by SCA3 (25.0%), SCA2 (21.9%), SCA1 (17.2%), SCA10 (4.7%) and DRPLA (3.1%); in 43% of the families, the subtype remained unidentified. SCA7 mutations displayed strong geographic aggregation in two independent founder foci, and SCA1 showed a very remote founder effect for a subset of families. SCA10 families were scattered across the country, but all had an identical in-phase haplotype carried also by Mexican, Brazilian and Sioux patients, supporting a very old common Amerindian origin. Prevalence for dominant SCAs in Venezuela was estimated as 1:25 000 nuclear families, provenances of which are either Caucasoid, African or Amerindian.

Huntington disease-like 2 (HDL2) in Venezuela: frequency and ethnic origin.

Huntington disease (HD) phenotypes without a HTT mutation are known as HD-like (HDL) syndromes and are caused by mutations in other loci. HDL2, almost indistinguishable from HD, is due to expansions in the Junctophilin 3 locus (JPH3) with a worldwide Sub-Saharan ethnic origin. Sixteen independent patients with involuntary movements, psychiatric disturbances and ataxia not having a HTT mutation were searched for loci PRNP (prion protein, HDL1), JPH3 (HDL2), ATN1 (dentatorubral-pallidoluysian atrophy), ATX2 (spinocerebellar ataxia 2) ATXN3 (spinocerebellar ataxia 3), and TBP (spinocerebellar ataxia 17=HDL4). Markers Duffy, Kell, Diego, D9S1120, plus six JPH3 intragenic single-nucleotide polymorphisms were tested to ascertain ethnic origin. Four unrelated choreic patients had an expanded allele at JPH3. Three of them carried the African marker Duffy null. All four families carried with the mutation the same haplotype most frequent in African populations; Amerindian alleles D9D1120*9 and Diego A; or Kell allele K were absent. HDL2 in Venezuela had a low, but higher relative frequency (2.6%) than that in other Caucasoid populations. It should be searched first in choreic patients not having HTT mutations. The most likely remote ethnic origin for all detected families was African.

The Regulatory Network Played by miRNAs During Normal Pregnancy and Preeclampsia: A Comparative Study.

BACKGROUND: Preeclampsia is a pregnancy-specific syndrome, characterized by hypertension, proteinuria, and edema. Affecting between 2% and 8% of gestations worldwide, it accounts for 10% to 15% of maternal deaths. Although its etiology remains unclear, it includes complex pathological processes involving microRNAs, small non-coding RNA molecules with post-transcriptional repression effects on target mRNAs. OBJECTIVE: To assess the expression of miRNAs during normal pregnancies and those complicated by preeclampsia, a sample of Venezuelan women were studied. METHOD: Nine placental microRNAs (hsa-miR- 20a-5p, 21-3p, 26a-5p, 181a-5p, 199a-5p, 210-3p, 222-5p, 223-3p, 424-3p) were measured in maternal plasma during the second and third trimesters of normal pregnancies, using a SYBR Green®-based real-time PCR, and compared the results against women affected by preeclampsia. RESULTS: All assessed miRNAs were detected in maternal plasma in pregnancies with and without preeclampsia. All except miR-222 were over-expressed during disease when compared to the second and to third-trimester controls. miR-20a, miR-21, miR-26a, and miR-223 were down-regulated in the third trimester in comparison to the second trimester in normal pregnancies. CONCLUSION: The variation of the miRNAs expression through normal pregnancies suggested their involvement in normal physiological pregnancy processes. In contrast, the significant deregulation of the nine studied miRNAs during preeclampsia indicated the involvement of their target genes in the pathogenesis of the disease. miR-199a and miR-21-3p showed the greatest changes in expression. This study shows for the first time the presence of miR-20a, miR-199, and miR-424 and the variations they undergo in the plasma of pregnant women with preeclampsia.

Marked geographic aggregation of acute intermittent porphyria families carrying mutation Q180X in Venezuelan populations, with description of further mutations.

Acute intermittent porphyria (AIP) caused by mutations in the hydroxymethylbilane synthase gene (HMBS), has been reported in almost all human populations, with varying frequencies. A founder effect for a few specific mutations in geographic regions where prevalence is high (Sweden, The Netherlands, Switzerland) has been established through haplotype analyses, while some other mutations (R26H, R26C) have been repeatedly reported in many populations with different genetic backgrounds. Epidemiological, biochemical and molecular data on AIP in Venezuela were gathered during the last two decades; 24 independent families with AIP were ascertained, based on a deficient HMBS activity and increased porphobilinogen (PBG) urinary excretion. Molecular analyses of coding and splicing regions were performed in 23 families, to establish disease-causing changes, and haplotype analyses were used to assess ancestral kinships between them. Changes were detected in 16 out of 23 families, 9 of them being different: R26H, R26C, c.87+5G>A, c.267-54_61delgaaggggt, R116W, Q180X, c.825+1G>A, c.913-1delG, and 3' UTR *277G>A. Seven mutations were found, each one in a single family; one mutation was present in two unrelated families, whereas mutation Q180X was shared by 7 independent kindreds, all of which had the same haplotype (-);T;A;T;G;T;A;G (3167delG; 3530T>C; 3581A>G; 3982T>C; 6479G>T; 7052T>C; 7064A>C; 7779G>A). Six out of seven different Q180X carrier families came from the same geographic focus (Santa Lucía, Miranda State). Dense geographic aggregation with one identical haplotype strongly suggests a remote founder phenomenon for these Venezuelan AIP families, carrying an unreported but most frequent mutation.

Hemoglobin S/hemoglobin City of Hope compound heterozygote with a SubSaharan genetic background and severe bone marrow hypoplasia.

Hemoglobin City of Hope (Hb CH) (HBB: c.208G>A, beta 69 (E13)Gly>Ser) is a rare, anomalous change. Seven independent carriers reported so far, had not displayed any hematological manifestations. The ethnic origin of the known instances is presumably heterogeneous, although they are mainly Mediterraneans or equatorial West Africans. We describe the case of a compound heterozygote in trans for Hb S (Glu6Val) and Hb City of Hope (Gly69Ser) in an anemic two year-old boy with a severe immune-deficient phenotype and fatal chronic parvovirus B19 infection. Haplotype with the Hb S was Bantu; while it was a mixed atypical Benin/Cameroon for Hb CH. Remote ancestral origin of the City of Hope mutation in this family seems to be SubSaharan African. The compound heterozygosis in trans for hemoglobins S and City of Hope, jointly with an unfavorable HBB control region background and a viral chronic infection, seemed the cause of the fatal outcome in the patient. When accompanied by other Hb deleterious mutations in trans, Hb CH should not be considered any longer as an innocuous or functionally silent variant.

[Influence of genetic factors on human sexual orientation. Review]. / Influencia de factores genéticos sobre la orientación sexual humana. Una revisión.

Human sexual orientation is a complex trait, influenced by several genes, experiential and sociocultural factors. These elements interact and produce a typical pattern of sexual orientation towards the opposite sex. Some exceptions exist, like bisexuality and homosexuality, which seem to be more frequent in males than females. Traditional methods for the genetic study of behavior multifactorial characteristics consist in detecting the presence of familial aggregation. In order to identify the importance of genetic and environmental factors in this aggregation, the concordance of the trait for monozygotic and dizygotic twins and for adopted sibs, reared together and apart, is compared. These types of studies have shown that familial aggregation is stronger for male than for female homosexuality. Based on the threshold method for multifactorial traits, and varying the frequency of homosexuality in the population between 4 and 10%, heritability estimates between 0.27 and 0.76 have been obtained. In 1993, linkage between homosexuality and chromosomal region Xq28 based on molecular approaches was reported. Nevertheless, this was not confirmed in later studies. Recently, a wide search of the genome has given significant or close to significant linkage values with regions 7q36, 8p12 and 10q26, which need to be studied more closely. Deviation in the proportion of X chromosome inactivation in mothers of homosexuals seems to favor the presence of genes related with sexual orientation in this chromosome. There is still much to be known about the genetics of human homosexuality.

Erratum to: Huntington disease mutation in Venezuela: age of onset, haplotype analyses and geographic aggregation.

In Table 2, a column heading was inadvertently omitted. Corrected table is as follows.

5-α-Reductase type 2 deficiency: is there a genotype-phenotype correlation? A review.

5-α-Reductase type 2 enzyme catalyzes the conversion of testosterone into dihydrotestosterone, a potent androgen responsible for male sexual development during the fetal period and later during puberty. Its deficiency causes an autosomal recessive disorder of sex development characterized by a wide range of under-virilization of external genitalia in patients with a 46,XY karyotype. Mutations in the SRD5A2 gene cause 5-α-Reductase deficiency; although it is an infrequent disorder, it has been reported worldwide, with mutational heterogeneity. Furthermore, it has been proposed that there is no genotype-phenotype correlation, even in patients carrying the same mutation. The aim of this review was to perform an extensive search in various databases and to select those articles with a comprehensive genotype and phenotype description of the patients, classifying their phenotypes using the external masculinization score (EMS). Thus, it was possible to objectively compare the eventual genotype-phenotype correlation between them. The analysis showed that for most of the studied mutations no correlation can be established, although the specific location of the mutation in the protein has an effect on the severity of the phenotype. Nevertheless, even in patients carrying the same homozygous mutation, a variable phenotype was observed, suggesting that additional genetic factors might be influencing it. Due to the clinical variability of the disorder, an accurate diagnosis and adequate medical management might be difficult to carry out, as is highlighted in the review.

GBA mutations in Gaucher type I Venezuelan patients: ethnic origins and frequencies.

Gaucher disease (GD), the most frequent lysosomal storage disease, is caused by heterogeneous mutations in the locus coding for glucocerebrosidase (GBA). It is an autosomal recessive disorder with different phenotypes of which the most frequent is the nonneuronopathic or type 1, prevalent worldwide. To date, more than 430 mutations have been described, but their frequency distribution varies in different populations with four, N370S, L444P, IVS2 + 1G > A and 84insG, being the most frequent ones. In Venezuela, 20 unrelated index cases with GD type I were assessed for GBA mutation detection and for their in-phase haplotype identification, to gather genetic epidemiological data on the disease in the country and of its eventual ethnic origin. Ten missense mutations and two complex alleles were identified. The most frequent were N370S (42.5%), L444P (20%), IVS2+1G > A (10%) and R48W (5%); mutations R120W, P245H, H311R, R496H, W36X and R433G which were carried by a single chromosome each one. Three geographical foci were identified, displaying mutation heterogeneity. N370S had multiple genetic origins, different from the Ashkenazi's; a single common remote ancestor for this mutation in the country was dismissed, according to the haplotype analysis. All mutations have a likely European Caucasoid descent.

LEP, LDLR and APOA4 gene polymorphisms and their relationship with the risk of overweight, obesity and chronic diseases in adults of the State of Sucre, Venezuela.

INTRODUCTION: Overweight, obesity and some chronic diseases have become more prevalent recently. It is well known that their causes may be genetic, epigenetic, environmental, or a mixture of these.  OBJECTIVE: To analyze the relationship between nine single nucleotide polymorphisms of genes LEP (rs2167270), LDLR (rs885765, rs688, rs5925, rs55903358, rs5742911) and APOA4 (rs5095, rs675, rs5110) with obesity-related phenotypes and other comorbidities.  MATERIAL AND METHODS: We recruited 144 adults (76 males and 68 females, with average ages of 29.93±8.29 and 32.49±11.15 years, respectively) in the State of Sucre, Venezuela. Clinical and anthropometric parameters were obtained. Genotype-risk associations were studied. We then compared the averages registered for anthropometric and biochemical variables previously adjusted for biological and environmental factors.  RESULTS: According to the body mass index, 38.9% of the individuals in the sample were overweight (25≤BMI≤29.9 kg/m2) and 20.1% were obese (BMI≥30 kg/m2). Genotype and allele frequencies did not differ statistically for groups with normal and high body mass index (overweight plus obesity). The association between LDLR rs5742911 ancestral genotype A/A and high risk condition related to HDL-cholesterol was the only one found to be significant (OR=2.944, 95% CI: 1.446-5.996; p=0.003). The difference in adjusted mean HDL-cholesterol for LDLR rs5742911 genotypes was statistically significant (p=0.005) (A/A: 41.50±14.81 mg/dL; A/G: 45.00±12.07 mg/dL; G/G: 47.17±9.43 mg/dL).  CONCLUSIONS: For most of the genetic variants studied, there was an association with the presence of overweight and obesity among ancestral genotype carriers, although this was not statistically significant. The rs5742911 polymorphism may be useful as an indicator of a risk of chronic diseases.

Most frequent mutation c.3402delC (p.Ala1135GlnfsX13) among Wilson disease patients in Venezuela has a wide distribution and two old origins.

Wilson disease is an infrequent autosomal recessive disorder caused by mutations in the ATP7B gene (13q14.3) producing pathologic phenotypes due to copper accumulation in critical tissues. The aim of the research was to probe Wilson disease genetic epidemiology in Venezuela, through the identification in diagnosed index cases, of ATP7B locus mutations, their geographic distribution, frequency, in-phase haplotypes and probable ethnic ancestry. During the last three decades 33 independent Wilson disease families from the country at large were ascertained and diagnosed through severely reduced ceruloplasmin activity, higher urinary copper excretion, and specific clinical signs. Molecular studies of the ATP7B gene were accomplished in 26 of the families. Disease prevalence was estimated as 1:94,000 families between 1985 and 2013, showing geographic aggregation in the state of Zulia with 1:27,000 families in it. DNA analysis in 26 families revealed 13 different mutations. The c.3402delC was the most frequent one (26.9%), presenting two independent in-phase haplotypes, both of likely European descent; which is followed by the not previously reported p.G691V (9.6%) and by the frequent European H1069Q (7.7%). Known mutations c.51 + 4A > T, c.1285 + 5G > T, M645R, T788I, V845SfsX28, T977M, L1088X, T1220M, R1319X and a novel P767L showed frequencies between 5.8 and 1.9%. Despite the ample mutation heterogeneity for Wilson disease in the country, the findings provide a diagnostic algorithm to ease mutation assessment in new patients; the predominant c.3402delC displayed wide geographic distribution and two genetic origins.

Polimorfismos de los genes LEP , LDLR , APOA4 y sus relaciones con el sobrepeso, la obesidad y el riesgo de enfermedades crónicas en adultos del estado Sucre, Venezuela / LEP , LDLR and APOA4 gene polymorphisms and their relationship with the risk of overweight, obesity and chronic diseases in adults of the State of Sucre, Venezuela

Introducción. La prevalencia del sobrepeso, la obesidad y algunas enfermedades crónicas no transmisibles ha aumentado; sus causas pueden ser genéticas, epigenéticas o ambientales, por lo cual es importante evaluar la variabilidad en estas interacciones. Objetivo. Analizar las relaciones entre nueve polimorfismos de nucleótido simple de los genes LEP (rs2167270), LDLR (rs885765, rs688, rs5925, rs55903358, rs5742911) y APOA4 (rs5095, rs675, rs5110), y los fenotipos asociados al sobrepeso, la obesidad y otras enfermedades concomitantes. Materiales y métodos. Se evaluaron parámetros clínicos y antropométricos en 144 sujetos del estado Sucre, Venezuela, 76 hombres y 68 mujeres , con medias de edad de 29,93±8,29 y 32,49±11,15 años, respectivamente. Se hizo la genotipificación de los polimorfismos seleccionados mediante enzimas de restricción; se estudiaron las asociaciones entre genotipo y riesgo, y se compararon los promedios de las medidas antropométricas y bioquímicas previamente ajustadas a variables biológicas y ambientales. Resultados. Según el índice de masa corporal (IMC), el 38,9 % de los individuos tenía sobrepeso (25=IMC=29,9 kg/m 2 ) y el 20,1 %, obesidad (IMC=30 kg/m 2 ) . Las frecuencias genotípicas y alélicas de los grupos con un índice de masa corporal normal y uno alto (sobrepeso y obesidad) resultaron similares. Solo se encontró asociación entre el genotipo ancestral A/A del rs5742911 y el riesgo alto por los niveles de la lipoproteína de alta densidad o colesterol HDL (OR=2,944, IC 95% 1,446-5,996; p=0,003). La diferencia entre los promedios corregidos de colesterol HDL para los genotipos del rs5742911 resultó significativa (p=0,005) (A/A: 41,50±14,81 mg/dl; A/G: 45,00±12,07 mg/dl; G/G: 47,17±9,43 mg/dl). Conclusión. En la mayoría de las variantes genéticas estudiadas, se registró la asociación con el sobrepeso y la obesidad de los genotipos ancestrales, aunque sin ser significativa. El polimorfismo rs5742911 podría resultar útil como indicador del riesgo de enfermedades crónicas.

Introduction: Overweight, obesity and some chronic diseases have become more prevalent recently. It is well known that their causes may be genetic, epigenetic, environmental, or a mixture of these. Objective: To analyze the relationship between nine single nucleotide polymorphisms of genes LEP (rs2167270) , LDLR (rs885765, rs688, rs5925, rs55903358, rs5742911) and APOA4 (rs5095, rs675, rs5110) with obesity-related phenotypes and other comorbidities. Material and methods: We recruited 144 adults (76 males and 68 females, with average ages of 29.93±8.29 and 32.49±11.15 years, respectively) in the State of Sucre, Venezuela. Clinical and anthropometric parameters were obtained. Genotype-risk associations were studied. We then compared the averages registered for anthropometric and biochemical variables previously adjusted for biological and environmental factors. Results: According to the body mass index, 38.9% of the individuals in the sample were overweight (25=BMI=29.9 kg/m 2 ) and 20.1% were obese (BMI=30 kg/m 2 ). Genotype and allele frequencies did not differ statistically for groups with normal and high body mass index (overweight plus obesity). The association between LDLR rs5742911 ancestral genotype A/A and high risk condition related to HDL-cholesterol was the only one found to be significant (OR=2.944, 95% CI: 1.446-5.996; p=0.003). The difference in adjusted mean HDL-cholesterol for LDLR rs5742911 genotypes was statistically significant (p=0.005) (A/A: 41.50±14.81 mg/dL; A/G: 45.00±12.07 mg/dL; G/G: 47.17±9.43 mg/dL). Conclusions: For most of the genetic variants studied, there was an association with the presence of overweight and obesity among ancestral genotype carriers, although this was not statistically significant. The rs5742911 polymorphism may be useful as an indicator of a risk of chronic diseases.

Huntington disease mutation in Venezuela: age of onset, haplotype analyses and geographic aggregation.

The aggregation of patients with Huntington's disease (HD) around Lake Maracaibo, Zulia State, Venezuela, is widely recognized, but the epidemiology of HD in the whole country is relatively unstudied. We have examined 279 individuals from 60 unrelated affected families residing in various areas of Venezuela for the presence of CAG repeats and other features associated with HD. The number of expanded repeats in 139 carriers varied from 35 to 112. Based on our examination of 71 symptomatic individuals, we developed a log-transformed regression equation, y= -0.0238x + 2.6616, to enable the prediction of age of onset in asymptomatic carriers. Intragenic haplotypes were constructed with two VNTRs (variable number of tandem repeats) and two SNPs (single nucleotide polymorphisms) in the promoter region as well as CCG repeat and Delta2642 polymorphisms to assess kinship between families. In 43 of 45 tested families, the haplotype on the mutated chromosome was 1;G;C;7;(A). The other haplotypes observed, 1;G;C;7;(B) and 4;G;C;7;(A), were of Peruvian and French origins, respectively. The geographic source of the first affected ancestor was assessed in 54 families from 15 different states. Residents of the states of Miranda, Lara and Táchira, excluding those of Zulia, had a mutated allele prevalence five- to ninefold higher than that of other areas. A low (approx. 1/200,000) prevalence, a wide-spread distribution with aggregation in some states and a likely remote European Caucasoid origin are defining epidemiologic features of HD in Venezuela.

IVIC syndrome is caused by a c.2607delA mutation in the SALL4 locus.

The IVIC syndrome described in 1980 in a large Venezuelan family, is an autosomal dominant condition characterized by upper limbs anomalies (radial ray defects, carpal bones fusion), extraocular motor disturbances, congenital bilateral non-progressive mixed hearing loss; other less consistent malformations include heart involvement, mild thrombocytopenia and leukocytosis (before age 50), shoulder girdle hypoplasia, imperforate anus, kidney malrotation or rectovaginal fistula. Since 2002, mutations in the SALL4 locus have been reported producing phenotypic features quite similar to those in IVIC syndrome; this gene was thus proposed as a candidate for the condition. A segregation analysis of four SNPs in exon 2 (c.1520T > G, c.1860A > G, c.2037C > T, and c.2392A > C) was carried out in 14 affected and in 15 normal family members. Haplotype T;A;C;A was found to always segregate with the disease. Sequencing the whole coding regions revealed one heterozygous base deletion in exon 3 (c.2607delA) causing a premature stop signal 44 codons downstream (p.Q869fsX44) which segregates with the phenotype, being absent in controls. The large number of affected individuals presumably carrying the same mutation (n = 26) with quite different degrees of involvement allowed a discussion about possible mechanisms for the SALL4 action. The finding of a SALL4 mutation in a family with such a wide pleiotropic spectrum proves that at least Okihiro, acro-renal-ocular and IVIC syndromes are allelic entities.

Hemoglobin S/hemoglobin city of hope compound heterozygote with a subsaharan genetic background and severe bone marrow hypoplasia

Hemoglobin City of Hope (HbCH) (HBB: c.208G>A, beta 69 (E13)Gly>Ser) is a rare, anomalous change. Seven independent carriers reported so far, had not displayed any hematological manifestations. The ethnic origin of the known instances is presumably heterogeneous, although they are mainly Mediterraneans or equatorial West Africans. We describe the case of a compound heterozygote in trans for Hb S (Glu6Val) and Hb City of Hope (Gly69Ser) in an anemic two year-old boy with a severe immune-deficient phenotype and fatal chronic parvovirus B19 infection. Haplotype with the Hb S was Bantu; while it was a mixed atypical Benin/Cameroon for Hb CH. Remote ancestral origin of the City of Hope mutation in this family seems to be SubSaharan African. The compound heterozygosis in trans for hemoglobins S and City of Hope, jointly with an unfavorable HBB control region background and a viral chronic infection, seemed the cause of the fatal outcome in the patient. When accompanied by other Hb deleterious mutations in trans, Hb CH should not be considered any longer as an innocuous or functionally silent variant.

La hemoglobina City of Hope (HbCH) (HBB: c.208G>A, beta 69 (E13)Gly>Ser) es una variante infrecuente, considerada como anómala. Ninguno de los siete heterocigotos simples, genéticamente no relacionados, reportados hasta ahora, ha mostrado hemopatología. El origen étnico de esos casos es presuntamente heterogéneo, pero la mayoría parece mediterráneo o africano-ecuatorial occidental. Se describe el caso de un niño de dos años de edad con fenotipo hipoplásico mieloeritroideo severo e infección crónica por parvovirus B19, heterocigoto compuesto en trans para las hemoglobinas S (Glu6Val) y City of Hope (Gly69Ser ). El haplotipo en fase con la Hb S fue Bantú, mientras que el de la Hb CH fue un combinado atípico Benin/Camerún. El origen ancestral remoto de la mutación City of Hope (y de la Hb S) en esta familia es africano subsahariano. La heterocigosis compuesta en trans para las hemoglobinas S y City of Hope y una secuencia génica predisponente en la región de control de HBB, conjuntamente con la infección por parvovirus B19 pueden ser la causa del curso fatal del paciente. En presencia de otras mutaciones de hemoglobina deletéreas, la Hb City of Hope no debiera ser considerada una variante inocua o funcionalmente silenciosa.

Influencia de factores genéticos sobre la orientación sexual humana: una revisión / Influence of genetic factors on human sexual orientation: review

La orientación sexual humana es un carácter complejo influido por varios genes, experiencias vivenciales y factores socioculturales. Estos factores interactúan y producen un patrón característico de orientación sexual hacia el sexo opuesto, pero existen excepciones, como la bisexualidad y la homosexualidad. Esta parece ser más frecuente en hombres que en mujeres. Es un carácter multifactorial. El método tradicional para el estudio genético de características del comportamiento consideradas multifactoriales es analizar si presentan agregación familiar. Para separar la importancia de los factores genéticos de los ambientales en esta agregación, se compara la concordancia para el carácter entre gemelos monocigóticos, dicigóticos y hermanos adoptados criados juntos. Estos estudios revelan que la agregación familiar es más evidente para la homosexualidad masculina que para la femenina. Utilizando el método del umbral para caracteres multifactoriales, y variando la frecuencia de homosexualidad en la población entre 4 y 10%, se han estimado valores de heredabilidad de la misma que oscilan entre 0,27 y 0,76. En 1993, utilizando métodos moleculares, se encontró ligamiento entre homosexualidad y la región cromosómica Xq28; sin embargo, estudios posteriores no lo confirman. Recientemente, la búsqueda amplia en el genoma mostró valores sugerentes o significativos de ligamiento en las regiones 7q36, 8p12 y 10q26, con genes candidatos de interés. La desviación en la proporción de inactivación del cromosoma X en las madres de homosexuales parece apoyar la presencia de genes relacionados con la orientación sexual en este cromosoma. Aún falta mucho por conocerse en relación a la genética de la homosexualidad humana.

Human sexual orientation is a complex trait, influenced by several genes, experiential and sociocultural factors. These elements interact and produce a typical pattern of sexual orientation towards the opposite sex. Some exceptions exist, like bisexuality and homosexuality, which seem to be more frequent in males than females. Traditional methods for the genetic study of behavior multifactorial characteristics consist in detecting the presence of familial aggregation. In order to identify the importance of genetic and environmental factors in this aggregation, the concordance of the trait for monozygotic and dizygotic twins and for adopted sibs, reared together and apart, is compared. These types of studies have shown that familial aggregation is stronger for male than for female homosexuality. Based on the threshold method for multifactorial traits, and varying the frequency of homosexuality in the population between 4 and 10%, heritability estimates between 0.27 and 0.76 have been obtained. In 1993, linkage between homosexuality and chromosomal region Xq28 based on molecular approaches was reported. Nevertheless, this was not confirmed in later studies. Recently, a wide search of the genome has given significant or close to significant linkage values with regions 7q36, 8p12 and 10q26, which need to be studied more closely. Deviation in the proportion of X chromosome inactivation in mothers of homosexuals seems to favor the presence of genes related with sexual orientation in this chromosome. There is still much to be known about the genetics of human homosexuality.