A family with hereditary extra-adrenal paragangliomas without evidence for mutations in the von Hippel-Lindau disease or ret genes

Tackling Dysfunction of Mitochondrial Bioenergetics in the Brain

Oxidative phosphorylation (OxPhos) is the basic function of mitochondria, although the landscape of mitochondrial functions is continuously growing to include more aspects of cellular homeostasis. Thanks to the application of -omics technologies to the study of the OxPhos system, novel features emerge from the cataloging of novel proteins as mitochondrial thus adding details to the mitochondrial proteome and defining novel metabolic cellular interrelations, especially in the human brain. We focussed on the diversity of bioenergetics demand and different aspects of mitochondrial structure, functions, and dysfunction in the brain. Definition such as 'mitoexome', 'mitoproteome' and 'mitointeractome' have entered the field of 'mitochondrial medicine'. In this context, we reviewed several genetic defects that hamper the last step of aerobic metabolism, mostly involving the nervous tissue as one of the most prominent energy-dependent tissues and, as consequence, as a primary target of mitochondrial dysfunction. The dual genetic origin of the OxPhos complexes is one of the reasons for the complexity of the genotype-phenotype correlation when facing human diseases associated with mitochondrial defects. Such complexity clinically manifests with extremely heterogeneous symptoms, ranging from organ-specific to multisystemic dysfunction with different clinical courses. Finally, we briefly discuss the future directions of the multi-omics study of human brain disorders.

Mitochondrial Structure and Bioenergetics in Normal and Disease Conditions

Mitochondria are ubiquitous intracellular organelles found in almost all eukaryotes and involved in various aspects of cellular life, with a primary role in energy production. The interest in this organelle has grown stronger with the discovery of their link to various pathologies, including cancer, aging and neurodegenerative diseases. Indeed, dysfunctional mitochondria cannot provide the required energy to tissues with a high-energy demand, such as heart, brain and muscles, leading to a large spectrum of clinical phenotypes. Mitochondrial defects are at the origin of a group of clinically heterogeneous pathologies, called mitochondrial diseases, with an incidence of 1 in 5000 live births. Primary mitochondrial diseases are associated with genetic mutations both in nuclear and mitochondrial DNA (mtDNA), affecting genes involved in every aspect of the organelle function. As a consequence, it is difficult to find a common cause for mitochondrial diseases and, subsequently, to offer a precise clinical definition of the pathology. Moreover, the complexity of this condition makes it challenging to identify possible therapies or drug targets.

New therapeutic and surgical approaches for sporadic and hereditary pheochromocytoma

Pheochromocytoma is a rare, surgically correctable cause of hypertension. Modern medical blockade has significantly improved patient survival and morbidity. The last decade has seen the identification of the genes responsible for several hereditary causes of pheochromocytoma. Evaluation of these patients has demonstrated different catecholamine profiles associated with the different syndromes. Genetic testing and new, more sensitive catecholamine tests are allowing better, earlier diagnosis of affected patients. Some patients with small tumors deemed nonfunctional by traditional methods may be safely observed until function is demonstrated. Laparoscopic surgery has supplanted the use of open surgery in the management of these tumors. Adrenocortical-sparing surgery may be performed using laparoscopy in patients with hereditary forms of pheochromocytoma.

Genetics of familial paragangliomas: past, present, and future

Genetic studies of hereditary paraganglioma tumors could increase the understanding of the biology of these fascinating tumors, with important clinical implications for diagnosis and treatment. This article focuses on the genetics of paraganglioma tumors, with limited reference to their general morphologic and clinical aspects. The paraganglioma tumor phenotype is defined. The genetic and physical mapping studies recently performed are summarized--studies that eventually led to the discovery of the gene for hereditary paraganglioma type 1 (PGL1). Finally, future directions stemming from the PGL gene discovery are described.

Gene mutations in the succinate dehydrogenase subunit SDHB cause susceptibility to familial pheochromocytoma and to familial paraganglioma

The pheochromocytomas are an important cause of secondary hypertension. Although pheochromocytoma susceptibility may be associated with germline mutations in the tumor-suppressor genes VHL and NF1 and in the proto-oncogene RET, the genetic basis for most cases of nonsyndromic familial pheochromocytoma is unknown. Recently, pheochromocytoma susceptibility has been associated with germline SDHD mutations. Germline SDHD mutations were originally described in hereditary paraganglioma, a dominantly inherited disorder characterized by vascular tumors in the head and the neck, most frequently at the carotid bifurcation. The gene products of two components of succinate dehydrogenase, SDHC and SDHD, anchor the gene products of two other components, SDHA and SDHB, which form the catalytic core, to the inner-mitochondrial membrane. Although mutations in SDHC and in SDHD may cause hereditary paraganglioma, germline SDHA mutations are associated with juvenile encephalopathy, and the phenotypic consequences of SDHB mutations have not been defined. To investigate the genetic causes of pheochromocytoma, we analyzed SDHB and SDHC, in familial and in sporadic cases. Inactivating SDHB mutations were detected in two of the five kindreds with familial pheochromocytoma, two of the three kindreds with pheochromocytoma and paraganglioma susceptibility, and 1 of the 24 cases of sporadic pheochromocytoma. These findings extend the link between mitochondrial dysfunction and tumorigenesis and suggest that germline SDHB mutations are an important cause of pheochromocytoma susceptibility.

Novel mutations and the emergence of a common mutation in the SDHD gene causing familial paraganglioma

Familial paragangliomas (PGL) are slow-growing, highly vascular, generally benign neoplasms, usually of the head and neck, that arise from neural crest cells. This rare autosomal dominant disorder is highly penetrant and influenced by genomic imprinting through paternal transmission. Timely detection of these tumors may afford the affected individual the opportunity to avoid the potential serious morbidity associated with surgical removal and the mortality that may accompany local and distant metastases. Linkage to two distinct chromosomal loci, 11q13.1 and 11q23, has been previously reported. Recently, germline mutations in SDHD, a mitochondrial complex II gene on chromosome 11q23, have been demonstrated. We evaluated members of seven families with PGL, five previously studied and shown to have linkage to chromosome 11q23. The entire coding region of the SDHD gene was sequenced and yielded four novel mutations and one mutation shared in three of our unrelated families. Novel mutations found included a truncating mutation in exon 2, as well as a missense mutation, a deletion, and an insertion in exon 4. Three of our families had a common mutation in exon 3 (P81L) that has been reported and thought to be a founder mutation. A restriction enzyme assay was developed for initial screening of this mutation. Molecular analysis is now available and recommended for presymptomatic diagnosis in those at-risk individuals and for confirmatory diagnosis in those having PGL.

Genetic analysis in the diagnosis of familial paragangliomas

OBJECTIVES

In the management of two related patients with multicentric glomus jugulare tumors, given the incidence of 1:30,000 with approximately 20% familial cases, our objective was to review the genetic characteristics and inheritance patterns of these tumors and to determine what molecular genetic screening possibilities exist for the phenotypically normal family members. In addition, our aim was to review the incidence of various multicentric paraganglioma (PGL) tumor location combinations.

METHODS

Molecular genetic linkage analysis testing was performed on the 2 patients and 14 other unaffected family members. We report the results of this screening and review the literature on the incidence and genetics of paragangliomas.

RESULTS

The inheritance pattern in the literature demonstrates autosomal dominant transmission with maternal imprinting (inactivation). The proclivity for multicentric origin increases to 26% in familial cases, as reflected in our patients. In addition to the two patients, four unaffected family members demonstrated the presence of the disease haplotype at chromosome band 11q23, which indicates a very high likelihood of developing a paraganglioma, given the highly penetrant nature of the disease.

CONCLUSIONS

It is clear that the familial PGL gene locus is situated at chromosome 11q23. The gene itself and its exact degree of penetrance, however, still await identification. Since early detection of paragangliomas reduces the incidence of morbidity and mortality, genotypic analysis as a screening tool in families of affected patients should play a front-line diagnostic role, leading to more timely and cost-effective patient management.

Comparative genomic hybridization reveals frequent losses of chromosomes 1p and 3q in pheochromocytomas and abdominal paragangliomas, suggesting a common genetic etiology

Pheochromocytomas and abdominal paragangliomas are rare, catecholamine-producing tumors that arise from the chromaffin cells derived from the neural crest. We used comparative genomic hybridization (CGH) to screen for copy number changes in 23 pheochromocytomas and 11 abdominal paragangliomas. The pattern of copy number changes was similar between pheochromocytomas and paragangliomas, with the most consistent finding being loss of 1cen-p31, which was detected in 28/34 tumors (82%). Losses were also found on 3q22-25 (41%), 11p (26%), 3p13-14 (24%), 4q (21%), 2q (15%), and 11q22-23 (15%), and gains were detected on 19p (26%), 19q (24%), 17q24-qter (21%), 11cen-q13 (15%), and 16p (15%). Losses of 1p and 3q were detected in the majority of tumors, whereas gains of 19p and q, 17q, and 16p were seen only in tumors with six or more CGH alterations. This progression of genetic events did not correspond with the conversion to a malignant phenotype. CGH alterations involving chromosome 11 were more frequent in the malignant tumors, compared with the benign tumors (9/12 versus 3/16). In summary, we propose that pheochromocytomas and abdominal paragangliomas, which share many clinical features, also have a common genetic origin and that the loss of 1cen-p31 represents an early and important event in tumor development.

Gastric stromal sarcoma, pulmonary chondroma, and extra-adrenal paraganglioma (Carney Triad): natural history, adrenocortical component, and possible familial occurrence

OBJECTIVE

To investigate the natural history of the triad of gastric stromal sarcoma, pulmonary chondroma, and extra-adrenal paraganglioma, a rare syndrome of unknown cause primarily affecting young women.

METHODS

Mayo Clinic records, the world literature, and the author's files were searched for patients with all or 2 of the 3 tumors.

RESULTS

Seventy-nine patients, 67 women and 12 men, were identified, 17 (22%) with the 3 tumors and 62 (78%) with 2 tumors. Forty-two (53%) had gastric and pulmonary tumors, the most common combination. The longest interval between detection of the first and second components was 26 years (mean, 8.4 years; median, 6 years). Follow-up ranged from 1 year to 49 years (mean, 20.6 years; median, 20 years). Sixty-four patients (81%) were alive, 19 (24%) apparently free of disease and 45 (57%) with residual or metastatic tumors. Thirty-two patients (41%) had had 1 or more local recurrences of the gastric sarcoma; the longest interval to first recurrence was 36 years. Twenty-one survivors (27%) had hepatic metastatic gastric sarcoma with follow-up of 1 year to 25 years (mean, 9.3 years; median, 7 years). Fifteen patients (19%) were dead, 10 (13%) of whom died of the disorder. Ten patients (13%) had nonfunctioning adrenocortical tumors. Two patients each had a sibling with 1 component of the triad.

CONCLUSIONS

The triad is a chronic, persistent, and indolent disease. Benign adrenocortical tumors are a component of the condition. The disorder may be familial.