Alteration of ornithine metabolism leads to dominant and recessive hereditary spastic paraplegia.
Brain. 2015 May 29;
Authors: Coutelier M, Goizet C, Durr A, Habarou F, Morais S, Dionne-Laporte A, Tao F, Konop J, Stoll M, Charles P, Jacoupy M, Matusiak R, Alonso I, Tallaksen C, Mairey M, Kennerson M, Gaussen M, Schule R, Janin M, Morice-Picard F, Durand CM, Depienne C, Calvas P, Coutinho P, Saudubray JM, Rouleau G, Brice A, Nicholson G, Darios F, Loureiro JL, Zuchner S, Ottolenghi C, Mochel F, Stevanin G
Hereditary spastic paraplegias are heterogeneous neurological disorders characterized by a pyramidal syndrome with symptoms predominantly affecting the lower limbs. Some limited pyramidal involvement also occurs in patients with an autosomal recessive neurocutaneous syndrome due to ALDH18A1 mutations. ALDH18A1 encodes delta-1-pyrroline-5-carboxylate synthase (P5CS), an enzyme that catalyses the first and common step of proline and ornithine biosynthesis from glutamate. Through exome sequencing and candidate gene screening, we report two families with autosomal recessive transmission of ALDH18A1 mutations, and predominant complex hereditary spastic paraplegia with marked cognitive impairment, without any cutaneous abnormality. More interestingly, we also identified monoallelic ALDH18A1 mutations segregating in three independent families with autosomal dominant pure or complex hereditary spastic paraplegia, as well as in two sporadic patients. Low levels of plasma ornithine, citrulline, arginine and proline in four individuals from two families suggested P5CS deficiency. Glutamine loading tests in two fibroblast cultures from two related affected subjects confirmed a metabolic block at the level of P5CS in vivo. Besides expanding the clinical spectrum of ALDH18A1-related pathology, we describe mutations segregating in an autosomal dominant pattern. The latter are associated with a potential trait biomarker; we therefore suggest including amino acid chromatography in the clinico-genetic work-up of hereditary spastic paraplegia, particularly in dominant cases, as the associated phenotype is not distinct from other causative genes.
PMID: 26026163 [PubMed - as supplied by publisher]
Key informations from this European study on HSP, published in Brain, may 29, 2015
Exome analysis enabled a network of 34 European researchers to pinpoint mutations of the ALDH18A1, a gene encoding enzyme , the so called P5CS enzyme, in 2 families with an autosomal recessive transmission and 3 independent families with an autosomal dominant transmission.
Of huge interest, the enzyme P5CS is instrumental for the metabolism of proline, arginine, citrulline and ornithine from glutamate (a non essential amino-acid). These amino-acids are involved in the urea cycle. A shortness of these amino-acids can cause a lot of symptoms.
Deficiency of this metabolism offers clues to find out a possible biomarker possibly opening towards a therapeutic approach.