SDHD mutations in head and neck paragangliomas result in destabilization of complex II in the mitochondrial respiratory chain with loss of enzymatic activity and abnormal mitochondrial morphology.
Hereditary head and neck paragangliomas are tumours associated with the autonomic nervous system. Recently, mutations in genes coding for subunits of mitochondrial complex II, succinate-ubiquinone-oxidoreductase (SDHB, SDHC, and SDHD), have been identified in the majority of hereditary tumours and a number of isolated cases. In addition, a fourth locus, PGL2, has been mapped to chromosome 11q13 in an isolated family. In order to characterize phenotypic effects of these mutations, the present study investigated the immunohistochemical expression of the catalytic subunits of complex II (flavoprotein and iron protein), SDH enzyme activity, and mitochondrial morphology in a series of 22 head and neck paragangliomas. These included 11 SDHD-, one SDHB-, two PGL2-linked tumours, and eight sporadic tumours. In the majority of the tumours (approximately 90%), the enzyme-histochemical SDH reaction was negative and immunohistochemistry of catalytic subunits of complex II showed reduced expression of iron protein and enhanced expression of flavoprotein. Ultrastructural examination revealed elevated numbers of tightly packed mitochondria with abnormal morphology in SDHD-linked and sporadic tumours. Immuno-electron microscopy showed localization of the flavoprotein on the remnants of the mitochondrial inner membranes, whereas virtually no signal for the iron protein was detected. These results indicate that the function of mitochondrial complex II is compromised in the majority of head and neck paragangliomas.
Douwes Dekker
P B
PB
Department of Otorhinolaryngology, Leiden University Medical Centre, Leiden, The Netherlands.
Hogendoorn
P C W
PC
Kuipers-Dijkshoorn
N
N
Prins
F A
FA
van Duinen
S G
SG
Taschner
P E M
PE
van der Mey
A G L
AG
Cornelisse
C J
CJ
D000328:Adult; D000368:Aged; D004252:DNA Mutational Analysis / Q000379:methods; D004273:DNA, Neoplasm / Q000235:genetics; D004579:Electron Transport / Q000235:genetics; D042963:Electron Transport Complex II / Q000235:genetics*; D005420:Flavoproteins / Q000032:analysis; D006258:Head and Neck Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D007501:Iron / Q000032:analysis; D007506:Iron-Sulfur Proteins / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D008854:Microscopy, Electron / Q000379:methods; D008875:Middle Aged; D008928:Mitochondria / Q000473:pathology*; D009363:Neoplasm Proteins / Q000235:genetics; D010235:Paraganglioma / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D021122:Protein Subunits; D013385:Succinate Dehydrogenase / Q000235:genetics
D004273:DNA, Neoplasm; D005420:Flavoproteins; D007506:Iron-Sulfur Proteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D021122:Protein Subunits; C491545:SDHD protein, human; D007501:Iron; D042963:Electron Transport Complex II; C108095:SDHB protein, human; D013385:Succinate Dehydrogenase