Modificación de la acción fisiológica de la FSH por las variantes genéticas de su receptor (FSHr) / No disponible

No disponible

Síndrome de Leigh causado por la mutación G14459A del ADN mitocondrial en una familia mexicana / Leigh syndrome caused by the mitochondrial DNA G14459A mutation in a mexican family

Introducción. El síndrome de Leigh es una enfermedad neurodegenerativa y progresiva, de aparición en la infancia, que está causada por defectos tanto en el genoma nuclear como en el mitocondrial. La mutación G14459A del ADN mitocondrial se ha asociado con anterioridad a la neuropatía óptica hereditaria de Leber y recientemente al síndrome de Leigh. Caso clínico. Niña mexicana de 10 meses de edad diagnosticada, después de un seguimiento clínico, neurológico y radiológico, de síndrome de Leigh. Se le realizó el análisis de mutaciones puntuales en el ADN mitocondrial asociadas a este síndrome, y se encontró la mutación G14459A en un porcentaje próximo a la homoplasmia y en heteroplasmia en la madre. El resto de familiares relacionados por vía materna carecen de la mutación. Conclusión. La mutación G14459A, aunque poco frecuente en la patología, debe de estudiarse en pacientes con síndrome de Leigh que no presentan las mutaciones puntuales más comunes (AU)

Introduction. Leigh syndrome is a neurodegenerative and progressive disease that appears usually in childhood due to defects in nuclear or mitochondrial genome. The mutation G14459A in mitochondrial DNA has been associated previously to Leber hereditary optic neuropathy and recently to Leigh syndrome. Case report. A 10 months-old Mexican girl diagnosed of Leigh syndrome. Molecular-genetic studies detected the mutation G14459A in a percentage close to homoplasmy and in low heteroplasmy in her mother. The rest of the maternally related family members analyzed were negative. Conclusion. The G14459A mutation, although not very frequently associated to Leigh syndrome, should be analyzed in patients that do not present the most common point mutations (AU)

[Leigh syndrome caused by the mitochondrial DNA G14459A mutation in a Mexican family]. / Síndrome de Leigh causado por la mutación G14459A del ADN mitocondrial en una familia mexicana.

INTRODUCTION: Leigh syndrome is a neurodegenerative and progressive disease that appears usually in childhood due to defects in nuclear or mitochondrial genome. The mutation G14459A in mitochondrial DNA has been associated previously to Leber hereditary optic neuropathy and recently to Leigh syndrome. CASE REPORT: A 10 months-old Mexican girl diagnosed of Leigh syndrome. Molecular-genetic studies detected the mutation G14459A in a percentage close to homoplasmy and in low heteroplasmy in her mother. The rest of the maternally related family members analyzed were negative. CONCLUSION: The G14459A mutation, although not very frequently associated to Leigh syndrome, should be analyzed in patients that do not present the most common point mutations.

NARP syndrome in a patient harbouring an insertion in the MT-ATP6 gene that results in a truncated protein.

BACKGROUND: Neurogenic muscle weakness, ataxia and retinitis pigmentosa (NARP) syndrome have been associated to m.8993T>G/C mutations in the subunit 6 of the ATP synthase (p.MT-ATP6). METHODS: We have performed a mutational screening of the mitochondrial DNA gene encoding for this protein in 62 patients with the disease, that do not carry any of the common mutations described to date. RESULTS: We report clinical and molecular data in one patient who harbours a de novo insertion in the MT-ATP6 gene that results in a truncated subunit. The mutation was heteroplasmic (85%) in muscle DNA and the BN-PAGE analysis showed a clear decrease in the amount of ATP synthase. CONCLUSION: Molecular analysis of NARP patients cannot be limited to the search of the m.8993T>G/C and either the ATP6 or the whole mtDNA should be sequenced.

Skeletal muscle mitochondrial DNA content in exercising humans.

Several weeks of intense endurance training enhances mitochondrial biogenesis in humans. Whether a single bout of exercise alters skeletal muscle mitochondrial DNA (mtDNA) content remains unexplored. Double-stranded mtDNA, estimated by slot-blot hybridization and real time PCR and expressed as mtDNA-to-nuclear DNA ratio (mtDNA/nDNA) was obtained from the vastus lateralis muscle of healthy human subjects to investigate whether skeletal muscle mtDNA changes during fatiguing and nonfatiguing prolonged moderate intensity [2.0-2.5 h; approximately 60% maximal oxygen consumption (Vo(2 max))] and short repeated high-intensity exercise (5-8 min; approximately 110% Vo(2 max)). In control resting and light exercise (2 h; approximately 25% Vo(2 max)) studies, mtDNA/nDNA did not change. Conversely, mtDNA/nDNA declined after prolonged fatiguing exercise (0.863 +/- 0.061 vs. 1.101 +/- 0.067 at baseline; n = 14; P = 0.005), remained lower after 24 h of recovery, and was restored after 1 wk. After nonfatiguing prolonged exercise, mtDNA/nDNA tended to decline (n = 10; P = 0.083) but was reduced after three repeated high-intensity exercise bouts (0.900 +/- 0.049 vs. 1.067 +/- 0.071 at baseline; n = 7; P = 0.013). Our findings indicate that prolonged and short repeated intense exercise can lead to significant reductions in human skeletal muscle mtDNA content, which might function as a signal stimulating mitochondrial biogenesis with exercise training.

An intragenic suppressor in the cytochrome c oxidase I gene of mouse mitochondrial DNA.

We report here the identification of a cell line containing single and double missense mutations in cytochrome c oxidase (COX) subunit I gene of mouse mitochondrial DNA. When present in homoplasmy, the single mutant displays a normal complex IV assembly but a significantly reduced COX activity, while the double mutant almost completely compensates the functional defect of the first mutation. We discuss the potential structural consequences of those mutations based on the modeled structure of mouse complex IV. Based on genetic, biochemical and molecular analyses of cultured mouse cells we infer that: (i) deleterious mutations can arise and become predominant; (ii) cultured cells can maintain several mtDNA haplotypes at stable frequencies; (iii) the respiratory chain has little spare COX capacity; and (iv) the size of a cavity in the vicinity of Val421 in CO I of animal COX may affect the function of the enzyme.

Variabilidad del DNA mitocondrial (clados y dosis genómica) y calidad seminal humana / Epidemiology of hepatitis C in health care workers. Routes of transmission

Son muchas las parejas que tienen problemas de fertilidad, siendo causas importantes, la astenozoospermia y la oligozoospermia. Resultados obtenidos por nuestro grupo, bloqueando la cadena respiratoria mitocondrial, demostraron que la motilidad espermática es dependiente del ATP mitocondrial. Diversos autores han encontrado que pacientes con diversas alteraciones mitocondriales muestran un mal funcionamiento de los órganos con gran demanda energética. Por otro lado, se ha establecido que los haplogrupos mitocondriales parecen predisponer a una mayor resistencia o susceptibilidad, según los casos, a determinadas enfermedades. Este trabajo, realizado con una población de 562 individuos procedentes de clínicas de reproducción asistida, muestra que el clado mitocondrial HV aporta un fondo genético resistente a la astenozoospermia. Además, ha podido observarse una disminución de la cantidad relativa de mtDNA conforme aumenta el porcentaje de espermatozoides progresivos y la concentración espermática. Todo ello permite afirmar que el genoma mitocondrial influye en la calidad seminal (AU)

Association between seminal plasma carnitine and sperm mitochondrial enzymatic activities.

Cellular parameters of the seminogram have been previously shown to correlate with L-carnitine concentration in the seminal fluid. Carnitine is involved in a variety of metabolic processes playing an important role in maintaining an active oxidative phosphorylation (OXPHOS). Recently, we have found a significant association between the specific activities of the respiratory chain complexes and the seminogram parameters and here we have studied the relationship between the spermatozoa OXPHOS activities and L-carnitine concentration in the seminal plasma. Carnitine, but not prostatic secretions, positive and significantly correlate with mitochondrial respiratory complex activities and the citric acid cycle enzymes citrate synthase and succinate dehydrogenase. It is remarkable that the ratios of the respiratory chain complexes to citrate synthase or succinate dehydrogenase, significant but negatively correlated with L-carnitine concentration. As carnitine in seminal plasma is secreted from the epididymis our results strongly suggest that relationships between carnitine secretion, seminal quality and OXPHOS activities could be because of a parallel response to the same regulatory event.

[Genetic diseases of the mitochondrial DNA in humans]. / Enfermedades genéticas del ADN mitocondrial humano.

Mitochondrial diseases are a group of disorders produced by defects in the oxidative phosphorylation system (Oxphos system), the final pathway of the mitochondrial energetic metabolism, resulting in a deficiency of the biosynthesis of ATP. Part of the polypeptide subunits involved in the Oxphos system are codified by the mitochondrial DNA. In the last years, mutations in this genetic system have been described and associated to well defined clinical syndromes. The clinical features of these disorders are very heterogeneous affecting, in most cases, to different organs and tissues and their correct diagnosis require precise clinical, morphological, biochemical and genetic data. The peculiar genetic characteristics of the mitochondrial DNA (maternal inheritance, polyplasmia and mitotic segregation) give to these disorders very distinctive properties. The English version of this paper is available at: http://www.insp.mx/salud/index.html.

[Diseases of mitochondrial DNA]. / Enfermedades del ADN mitocondrial.

INTRODUCTION: Human diseases caused by disorders of the mitochondrial metabolism have been described more than 30 years ago. Some of these are associated to defects in the oxidative phosphorylation system (OXPHOS system), the final pathway of the mitochondrial energetic metabolism, that leads to the synthesis of ATP. DEVELOPMENT: Part of the polypeptide subunits involved in the OXPHOS system are codified by the mitochondrial DNA (mtDNA). In the last 12 years, mutations (point mutations or deletions) in the mtDNA have been described and associated to well defined clinical syndromes caused by defects in the OXPHOS system. The clinical features of these diseases are very heterogeneous affecting in most cases to a great variety of organs and tissues. CONCLUSIONS: The correct diagnosis of these mitochondrial disorders require precise clinical, morphological, biochemical, and genetic data. The rapid advances in genetic analysis allow the rapid detection of mutations, even before the obtention of other type of analysis.

Human mtDNA haplogroups associated with high or reduced spermatozoa motility.

A variety of mtDNA mutations responsible for human diseases have been associated with molecular defects in the OXPHOS system. It has been proposed that mtDNA genetic alterations can also be responsible for sperm dysfunction. In addition, it was suggested that if sperm dysfunction is the main phenotypic consequence, these mutations could be fixed as stable mtDNA variants, because mtDNA is maternally inherited. To test this possibility, we have performed an extensive analysis of the distribution of mtDNA haplogroups in white men having fertility problems. We have found that asthenozoospermia, but not oligozoospermia, is associated with mtDNA haplogroups in whites. Thus, haplogroups H and T are significantly more abundant in nonasthenozoospermic and asthenozoospermic populations, respectively, and show significant differences in their OXPHOS performance.

Enfermedades del ADN mitocondrial / Diseases of the mitochondrial DNA

Introducción. Desde hace más de 30 años se conocen diversas anomalías del metabolismo mitocondrial que producen enfermedades humanas. Entre ellas se encuentran los defectos en el sistema de fosforilación oxidativa (sistema OXPHOS), la ruta final del metabolismo energético mitocondrial que conduce a la síntesis de ATP. Desarrollo. Este sistema presenta la particularidad de que una parte de las subunidades proteicas que lo componen están codificadas en el ADN mitocondrial. En los últimos 12 años se han descrito una serie de mutaciones (puntuales o deleciones) en el ADN mitocondrial que se han asociado con síndromes clínicos bien definidos originados por defectos en el sistema OXPHOS. Los caracteres clínicos de estas enfermedades son muy heterogéneos y, excepto en algún caso, afectan a gran variedad de órganos y tejidos. Conclusiones. El diagnóstico preciso de este grupo de trastornos requiere la obtención de datos clínicos, morfológicos, bioquímicos y genéticos. La utilización de técnicas sencillas de genética molecular permite la detección rápida de mutaciones, incluso antes de que puedan realizarse otros tipos de análisis (AU)

Seminal quality correlates with mitochondrial functionality.

Oligozoospermia is an important manifestation of male subfertility and very little attention has been paid to study a possible relationship between the total number of ejaculated spermatozoa and mitochondrial functionality. In this work we report a direct correlation between spectrophotometrically measured mitochondrial enzyme activities (citrate synthase and respiratory complex I, II, I+III, II+III and IV) and seminogram parameters (sperm motility, vitality and cell concentration). In addition, total ejaculated spermatozoa correlate much better with the nuclear-encoded citrate synthase and complex II than with the mitochondrial-encoded complex I, III and IV activities. Furthermore, total number of spermatozoa has a significant but negative correlation with the ratios of complex I, complex III and complex IV to complex II (and citrate synthase). These ratios are significantly higher in aged subjects emphasizing the physiological relevance of this observation. These results suggest that the simultaneous increase of the number of ejaculated spermatozoa and the mitochondrial enrichment of citrate synthase and complex II are both parallel responses to the same regulatory events.

Direct and highly species-specific detection of pork meat and fat in meat products by PCR amplification of mitochondrial DNA.

Highly species-specific primers for pork D-loop mtDNA have been designed. Use of these and restrictive PCR amplification conditions has improved a reliable and rapid method for detecting a PCR-amplified 531 bp band from pork. It has been proved useful for detecting both pork meat and fat in meat mixtures, including those dry-cured and heated by cooking. Absence of response in PCR-amplified samples or mixtures from bovine, ovine, chicken, and human was also demonstrated. Furthermore, wild boar and pork samples can be also easily distinguished by a simple AvaII restriction analysis.

Respiratory chain enzyme activities in spermatozoa from untreated Parkinson's disease patients.

We studied respiratory chain enzyme activities in spermatozoa homogenates from 12 untreated Parkinson's disease (PD) male patients and from 23 age matched healthy male controls. When compared with controls, PD patients showed significantly lower specific activities for complexes I+ III, II+III, and IV. However, citrate synthase corrected activities were similar in patients and controls. Values for enzyme activities in the PD group did not correlate with age at onset, duration, scores of the Unified Parkinson's Disease Rating Scales and Hoehn and Yahr staging. These results suggest that this tissue cannot be used to develop a diagnostic test for PD.

Direct regulation of mitochondrial RNA synthesis by thyroid hormone.

We have analyzed the influence of in vivo treatment and in vitro addition of thyroid hormone on in organello mitochondrial DNA (mtDNA) transcription and, in parallel, on the in organello footprinting patterns at the mtDNA regions involved in the regulation of transcription. We found that thyroid hormone modulates mitochondrial RNA levels and the mRNA/rRNA ratio by influencing the transcriptional rate. In addition, we found conspicuous differences between the mtDNA dimethyl sulfate footprinting patterns of mitochondria derived from euthyroid and hypothyroid rats at the transcription initiation sites but not at the mitochondrial transcription termination factor (mTERF) binding region. Furthermore, direct addition of thyroid hormone to the incubation medium of mitochondria isolated from hypothyroid rats restored the mRNA/rRNA ratio found in euthyroid rats as well as the mtDNA footprinting patterns at the transcription initiation area. Therefore, we conclude that the regulatory effect of thyroid hormone on mitochondrial transcription is partially exerted by a direct influence of the hormone on the mitochondrial transcription machinery. Particularly, the influence on the mRNA/rRNA ratio is achieved by selective modulation of the alternative H-strand transcription initiation sites and does not require the previous activation of nuclear genes. These results provide the first functional demonstration that regulatory signals, such as thyroid hormone, that modify the expression of nuclear genes can also act as primary signals for the transcriptional apparatus of mitochondria.

Reduced mitochondrial DNA transcription in senescent rat heart.

We studied the effect of senescence on mitochondrial DNA (mtDNA) transcription with an in organello system using intact isolated rat heart mitochondria. A comparison of the electrophoretic patterns of mtDNA transcription products in young, adult and senescent rats showed an age-related reduction in newly-synthesized mitochondrial RNAs that reflects a decrease in the synthesis rate. These results correlate with the enzyme activities of the oxidative phosphorylation complexes I and IV, that are partially encoded by the mitochondrial genome. In addition, an age-related increase in the protein carbonyl content of the mitochondrial membranes was observed in senescent mitochondria suggesting an accumulation of mitochondrial oxidative damage. This reduction in the mtDNA transcriptional rate in the heart of senescent animals suggests that this could be one of the molecular bases underlying senescence of the myocardium.

[Human mitochondrial genetic system]. / Sistema genético mitocondrial humano.

The mitochondria are subcellular organelles devoted to energy production in form of ATP that contain their own genetic system. Mitochondrial DNA codify a small, but extremely important, number of polypeptides of the respiratory chain. The other mitochondrial proteins are encoded in the nucleus. Therefore, mitochondrial biogenesis require the coordinated expression of nuclear and mitochondrial genetic systems. The gene arrangement in mitochondrial DNA is extremely compact with the tRNA genes interspersed with the rRNA and protein-coding genes. This organization has its precise counterpart in the mode of expression and distinctive structural features of the RNAs. Both mitochondrial DNA strands are transcribed as a whole in the form of three polycistronic molecules that are later cut by specific enzymes that recognize the 5' and 3' end of the tRNA sequences, to produced the mature rRNA, mRNA and tRNA. The mitochondrial coded mRNAs are translated into proteins by a mitochondrial specific protein-synthesizing machinery. The genetics of the mitochondrial DNA differs from that of the nuclear DNA in several features. In particular, the mitochondrial genome is inherited from the mother that transmit their mitochondrial DNA to all her offsprings. Another characteristic of this genome is its tendency to mutate more frequently than the nuclear DNA. This provides a powerful tool for studying the evolution of man.

Correlation of sperm motility with mitochondrial enzymatic activities.

Until now, little attention has been paid to the contribution of mitochondrial dysfunction to germinal tissue disorders. The target of this study was to investigate the relationship between sperm motility and mitochondrial respiratory chain enzyme activities. The results obtained showed that semen samples of control individuals (n = 33) have substantially higher activities of complexes I, II, and IV compared with those of asthenozoospermic subjects (n = 86). Moreover, a direct and positive correlation was found in the whole population studied between spermatozoa motility and all the mitochondrial respiratory complex activities assayed (I, II, I+III, II+III, and IV). The ratio of these enzymes to citrate synthase (a reliable enzymatic marker of mitochondrial volume) activities did not correlate with sperm motility. This suggests that motility depends largely on the mitochondrial volume within the sperm midpiece. These observations could be of physiopathological relevance because they suggest that factors affecting the mitochondrial energy production could be then responsible for particular cases of idiopathic asthenozoospermia.

Viability of ram spermatozoa in relation to the abstinence period and successive ejaculations.

For successful fertilization, a functionally constituted sperm plasma membrane is necessary, and this is clearly dependent on the sperm maturation process. The latter involves a series of complex changes which result from a sequence of events occurring at different points within the epididymis. The transit time through the epididymis can be influenced by external factors such as sexual stimulus and ejaculatory frequency. The present work was undertaken to determine changes in ram sperm viability and other sperm quality characteristics in relation to ejaculatory frequency. Three successive ejaculates were collected from rams during three different abstinence periods (collected every day, every 2 days and every 3 days). Cell viability (membrane integrity determined by fluorescence staining), progressive individual motility, and other in vitro parameters of sperm quality were evaluated. Second ejaculates showed the highest cell viability of the three periods studied, and increased as the abstinence period lengthened. The maximum proportion of viable cells (average 60%) was obtained in the second ejaculate after an abstinence period of 3 days. Likewise, overall and progressive individual motilities were higher in second ejaculates, the maximum value being 70% after 3 days of abstinence. The percentage of damaged or acrosome-reacted spermatozoa was greater after 1 day of abstinence than after the other periods analysed, whereas the first ejaculate showed the highest value in all periods. Differences in ejaculate volume were correlated strongly with both variables considered (abstinence period and ejaculate number). In the third ejaculate, about 27% more volume was obtained after 3 days of abstinence than after abstinence for 1 or 2 days. Sperm concentration increased significantly as the abstinence period lengthened, and also decreased significantly with ejaculate number in all cases. Therefore, the total number of spermatozoa in the ejaculate was clearly dependent on the abstinence period and the ejaculate number. In conclusion, the results obtained suggest that using the second and/or a mixture of second and third ejaculates would improve the results in artificial insemination and in fertility studies. In addition, the use of better quality semen would facilitate progress in semen cryopreservation studies.