Transcript pps lecture
Genetic Diagnostic of Leukodystrophy Massoud Houshmand (Ph.D) Special Medical Center www.specialmedicallab.com Massoud Houshmand Clinical Presentations • Intoxication – Urea cycle defects • Energy Failure – Mitochondrial disease – Glycogen storage disease • Complex Molecule – Lysosomal storage disease – Glycogen storage disease – Peroxisomal storage disorders Diseases that Cause Leukodystrophy Some examples • Adrenoleukodystrophy • Metachromatic leukodystrophy • Tay-Sachs • Krabbe • Multiple Sulfatase Deficiency (Austin Disease) • Canavan • Alexsander • Pelizaeus-Merzbacher Adrenoleukodystrophy/ Adrenomyeloneuropathy Adrenoleukodystrophy/ Adrenomyeloneuropathy • Most common peroxisomal disorder (1/20,000) • Mutation in ABCD on Xq28 leads to defect in peroxisomal uptake of VLCFA • ALD: progressive neurologic disorder that begins at 512 years – – – – – Boys with new onset school difficulties & ADHD Visuo-spatial deficits and hearing loss Spasticity, ataxia, maybe seizures Hypoglycemia, salt losing, hyperpigmentation Rx: steroids, presymptomatic stem cell transplant, Lorenzo’s oil ineffective (oleic and erucic acids) • AMN: early adulthood progressive spastic paraparesis, cerebral demyelination (males) Gene ABCD1 Mutation Detection Frequency by Test Method Heterozyg Males ous Females Test Method Mutations Detected Sequence analysis Sequence 99% variants (Multi)exonic or whole-gene del/dup ~6% Del/dup analysis 93% ~6% Gene Symbol Chromosom Protein al Locus Name Locus Specific ABCD1 Xq28 ABCD1 @ ABCD1 LOVD ALD mutation database (ABCD1) X-linked Adrenoleuko dystrophy Database (ABCD1) ATP-binding cassette subfamily D member HGMD DNA Nucleotide Change Protein Amino Acid Change c.1415_1416delAG (c.1801_1802delAG) p.Gln472ArgfsTer83 (fsGlu471) Metachromatic Leukodystrophy Metachromatic Leukodystrophy • AR defect of arylsulfatase-A • Leukodystrophy as well as disease of adrenal glands, kidneys, pancreas, liver Metachromatic Leukodystrophy • 3 Presentations – Late infantile (18-24 months) • Gait disturbance, hypotonia to hypertonia, regression, involuntary movements, neuropathy, cherry red spot – Juvenile (4-10 years) • Bradykinesia, poor school performance, ataxia, movement disorder, neuropathy, slower progression – Adult • After puberty get personality and mental changes, cortical and cerebellar regression to frank dementia in third to fourth decade Metachromatic Leukodystrophy Sandhoff GM 1 Ganglio sidosis Taysachs Fabry Lactosyl Ceramidosis Gaucher Niemann-Pick Krabbe Metachromatic Leukodystrophy Familial Lipogranulomaltosis Form Late infan tile Early juve nile Late juve nile Adult Age at Onset (yrs) Freque ncy Neurocognitive Deficit Progression <4 Most com mon Motor milestones lost, neurocognitive functions lost Death within 5-6 yrs 4-6 Less com mon Motor milestones lost, learning and behavior impaired Death within 10-15 yrs 6-16 >16 Rare Personality changes, behavioral changes, dementia, psychosis, decreased school or work performance Slow Rare Personality changes, behavioral changes, dementia, psychosis, decreased school or work performance Slow Molecular Genetic Testing Used in Arylsulfatase A Deficiency Mutation Detection Rate Mutations Test Methods Detected Infantile Juvenile onset onset mld 36% to 40% to Targeted mut alleles 50% 50% ation analysi s Pd allele >90% Sequence ARSA analysis/mut sequence ation alterations scanning 90-95% Adult onset 73% to 90% Molecular Genetics of Arylsulfatase A Deficiency Gene Symbol Chromosomal Locus Protein Name ARSA 22q13.3-qter Arylsulfatase A Gene Name Gene symb ol Location DNA kb Exon RNA bp Protein s kDa Amino Acide arylsulfatase A ARSA 22q13.33 3,12 8 2039 53.6 507 Because of the interference of the enzyme arylsulfatase B (ARSB) in the most commonly used assays of ARSA enzymatic activity , an ARSA enzyme activity in the 5-20% range cannot establish or eliminate the diagnosis of MLD; therefore, one or more of the following additional tests is necessary: Molecular genetic testing of the ARSA gene Urinary sulfatide excretion Other evidence of sulfatide storage, such as Tay-Sachs Gm2 Gangliosidosis • Tay-sachs disease – hexosaminidase A • Sandhoff disease – hexosaminidase A&B Sandhoff GM 1 Ganglio sidosis Taysachs Fabry Lactosyl Ceramidosis Gaucher Niemann-Pick Krabbe Metachromatic Leukodystrophy Familial Lipogranulomaltosis Hexosaminidase A Deficiency Sandhoff GM 1 Ganglio sidosis Taysachs Fabry Lactosyl Ceramidosis Gaucher Niemann-Pick Krabbe Metachromatic Leukodystrophy Familial Lipogranulomaltosis Gene • HEXA, the gene encoding the alpha subunit of the HEX A enzyme, is the only gene associated with hexosaminidase A deficiency. Molecular genetic testing: Clinical uses • Confirmatory diagnosis in symptomatic individuals with borderline enzyme activity • Prenatal diagnosis when both parental mutations are known Heterozygotes Test Method Targeted mutation analysis Mutations Detected Obligate Screening Jewish NonJewish Jewis Nonh Jewish +TATC1278 81% 32% 80% 8% +1 IVS 12 15% 0 9% 0 +1 IVS 9 0 14% 0 10% G269S 2% 0 3% 5% R247W 0 0 2% 32% R249W 0 0 0 4% All of the above 98% 46% 94% 59% Gene Symbol HEXA Chromosoma l Locus 15q23-q24 Protein Name Betahexosaminidase alpha chain Gene Review Gene Name Gene symbol Location DNA hexosaminida se A HEXA 15q23q24 32,6 k b HEXA Exon RNA 14 Protein 2255 b 60.7 kDa p Amino Acide 529 • In Tay-Sachs a mutation occurs which inhibits the productio of necessary proteins by Hex A • The loss of these necessary enzymes will cause brain damage Krabbe Disease Krabbe • AR defect of galactocerebroside-betagalactosidase on chromosome 14 • Pure neurologic condition • Onset at 3-8 months of age • Irritability, intermittent fevers, heightened startle reflex, feeding problems • Develop seizures, opisthotonus • Deafness and blindness by 9 months • MRI: KRABBE DISEASE Sandhoff GM 1 Ganglio sidosis Taysachs Fabry Lactosyl Ceramidosis Gaucher Niemann-Pick Krabbe Metachromatic Leukodystrophy Familial Lipogranulomaltosis Test Method Mutations Detected Mutation Detection Rate GALC 30-kb deletion Infantile Krabbe disease: varies by ethnicity Targeted mutation analysis GALC 809G>A mutation Sequence analysis GALC sequence variants Late-onset Krabbe disease: approximately 50% have one copy of the mutation ~100% Gene Symbol GALC Chromosomal Locus Protein Name 14q31 Galactocerebrosidase Nucleotide Change Amino Acid Change Percent of All Alleles 502C>T p.R168C 4%-5% 694G>A p.D232N 8%-10% 1637T>C p.I546T 30%-40% 502C>T + 1637T>C p.R168C + p.I546T <2% Percent of Mutant Alleles Nucleotide Change 40%-50% 30-kb deletion 5%-8% 1538C>T 5%-8% 1652A>C 2%-5% 1424delA 1%-2% 809G>A 32%-47% Multiple Sulfatase Deficiency (Austin Disease) Proptosis Ichthyosis hepatosplenomegaly Multiple Sulfatase Deficiency • AR, mutations in sulfatase-modifying factor-1 gene (SUMF1) on 3p26 • Austria: 1 in 1.4 million individuals • Affects 12 sulfatase enzymes – Post-translation modification defect in which cystein residue of enzyme is not activated – Defect in enzyme that causes oxidation of a thiol group in cysteine to generate an alpha-formylglycine residue – Alpha-formylglycine residue may accept the sulfate during sulfate ester cleavage by hydrolysis – Examples: arylsulfatase, steroid sulfatase, heparan sulfatase, Nacetylglucosamine-6-sulfatase Multiple Sulfatase Deficiency • 3 phenotypes – Neonatal MSD: severe mucopolysaccharidosis – Late infantile MSD: late-onset MLD – Juvenile MSD • Combined features of MLD, Hunter, Sanfilippo A, Morquio, Maroteaux-Lamy, Xlinked ichthyosis Canavan Canavan • AR deficiency of asparto-acylase • Macrocephaly, lack of head control, and developmental delays by the age of three to five months • Develop severe hypotonia and failure to achieve independent sitting, ambulation, or speech • Hypotonia eventually changes to spasticity • Life expectancy is usually into the teens • Diagnosis of Canavan disease relies upon demonstration of very high concentration of N-acetyl aspartic acid (NAA) in the urine Canavan disease Courtesy Dr Isabelle Desguerre, Paris Necker Hospital gene Symbol ASPA Test Method Mutations Detected Mutation Detection Frequency by Test Method NonAshkenazi Ashkenazi Jewish Jewish p.Glu285Ala, 98% p.Tyr231X 3% p.Ala305Glu 1% 30%-60% Targeted mutation analysis Panel Sequence analysis Sequence variants NA Large genomic Deletion / deletions/duplications duplication NA comprising one or analysis more exons 87% Unknown (<10%) Protein Amino Acid DNA Nucleotide Change Change c.433-2A>G -- c.693C>A p.Tyr231X c.854A>C p.Glu285Ala c.863A>G p.Tyr288Cys c.914C>A p.Ala305Glu Alexander Disease • AD mutation in GFAP at 17q21.31 • Onset at around 6 months (birth – 2 yrs) • Psychomotor regression, spasticity and seizures • Juvenile patients have ataxia and spasticity • Adult patients have MS-like presentation • Diffuse demyelination, especially in frontal lobes Alexander Disease Mutation Detection Mutations Frequency Detected by Test Method Gene Test Method GFAP Sequence Sequence 97% analysis variants Gene Symbol GFAP Chromoso Protein mal Locus Name 17q21.31 Glial fibrillary acidic protein Locus HGMD Specific Human GFAP Intermedia te Filament Database GFAP GFAP database DNA Nucleotide Change (Alias 1) Protein Amino Acid Change c.209G>A c.208C>T c.218T>C c.226C>T c.230A>G c.235C>T c.236G>A p.Arg70Gln p.Arg70Trp p.Met73Thr p.Leu76Phe p.Asn77Ser p.Arg79Cys p.Arg79His c.256_259delinsGAGT p.Glu86_Glu87delinsGluGlu c.290T>C p.Leu97Pro c.376_381dupGCGGCT p.Arg126_Leu127dup c.613G>A c.628G>A c.715C>T c.716G>A c.716G>C c.731C>T p.Glu205Lys p.Glu210Lys p.Arg239Cys p.Arg239His p.Arg239Pro p.Ala244Val c.1047_1048insCACTTG p.Tyr349_Gln350insHisLeu c.1055T>C c.1076T>C c.1117G>A c.1178G>T p.Leu352Pro p.Leu359Pro p.Glu373Lys p.Ser393Ile c.1249delG p.Asp417MetfsTer15 Pelizaeus-Merzbacher Pelizaeus-Merzbacher • Xq22 mutation in proteolipid protein 1 (PLP1) • Onset in first few months of life with rotary head movements, rotary nystagmus, & motor delay • Then ataxia, tremor, choreoathetosis, spasticity • Seizures • Optic atrophy and ocular impairments • MRI: Reversal of gray-white signal due to diffuse dymyelination Pelizaeus-Merzbacher Thanks for your patients and attention