Molecular analysis of NPC1 and NPC2 gene in 34 Niemann-Pick C Italian patients: identification and structural modeling of novel mutations.
Niemann-Pick C, the autosomal recessive neuro-visceral disease resulting from a failure of cholesterol trafficking within the endosomal-lysosomal pathway, is due to mutations in NPC1 or NPC2 genes. We characterized 34 unrelated patients including 32 patients with mutations in NPC1 gene and two patients in NPC2 gene. Overall, 33 distinct genotypes were encountered. Among the 21 unpublished NPC1 alleles, 15 were due to point mutations resulting in 13 codon replacements (p.C100S, p.P237L, p.R389L, p.L472H, p.Y634C, p.S636F, p.V780G, p.Q921P, p.Y1019C, p.R1077Q, p.L1102F, p.A1187V, and p.L1191F) and in two premature stop codons (p.R934X and p.Q447X); a new mutant carried two in cis mutations, p.[L648H;M1142T] and four other NPC1 alleles were small deletions/insertions leading both to frame shifts and premature protein truncations (p.C31WfsX26, p.F284LfsX26, p.E1188fsX54, and p.T1205NfsX53). Finally, the new intronic c.464-2A>C change at the 3' acceptor splice site of intron 4 affected NPC1 messenger RNA processing. We also found a new NPC2 mutant caused by a change of the first codon (p.M1L). The novel missense mutations were further investigated by two bioinformatics approaches. Panther proein classification system computationally predicted the detrimental effect of all new missense mutations occurring at evolutionary conserved positions. The other bioinformatics approach was based on prediction of structural alterations induced by missense mutations on the NPC1 atomic models. The in silico analysis predicted protein malfunctioning and/or local folding alteration for most missense mutations. Moreover, the effects of the missense mutations (p.Y634C, p.S636F, p.L648H, and p.V780G) affecting the sterol-sensing domain (SSD) were evaluated by docking simulation between the atomic coordinates of SSD model and cholesterol.
Fancello
Tatiana
T
Dipartimento di Scienze Biomediche, Università di Modena e Reggio Emilia, Modena, Italy.
Dardis
Andrea
A
Rosano
Camillo
C
Tarugi
Patrizia
P
Tappino
Barbara
B
Zampieri
Stefania
S
Pinotti
Elisa
E
Corsolini
Fabio
F
Fecarotta
Simona
S
D'Amico
Adele
A
Di Rocco
Maja
M
Uziel
Graziella
G
Calandra
Sebastiano
S
Bembi
Bruno
B
Filocamo
Mirella
M
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D007223:Infant; D047908:Intracellular Signaling Peptides and Proteins; D007558:Italy; D008562:Membrane Glycoproteins / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D000077296:Niemann-Pick C1 Protein; D052556:Niemann-Pick Disease, Type C / Q000235:genetics* / Q000503:physiopathology; D010641:Phenotype; D011487:Protein Conformation; D033921:Vesicular Transport Proteins; D055815:Young Adult
D002352:Carrier Proteins; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; C106881:NPC1 protein, human; C104585:NPC2 protein, human; D000077296:Niemann-Pick C1 Protein; D033921:Vesicular Transport Proteins