maple syrup urine disease msud by jenny morrison 836445 n.
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Maple Syrup Urine Disease (MSUD) By Jenny Morrison (836445)

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Maple Syrup Urine Disease (MSUD) By Jenny Morrison (836445)

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Maple Syrup Urine Disease (MSUD) By Jenny Morrison (836445)

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  1. Deficiency in branched chain alpha-keto acid dehydrogenase complex (BCKAD) – located in mitochondrial inner membrane Caused by mutation in 4 possible genes BCKDHA, BCKDHB, DBT, and DLD that encode for the BCKAD Results in defect in metabolism of branched chain amino acids (BCAA): Valine, Leucine and Isoleucine Accumulation of BCAA and their keto acid derivatives 5 clinical subtypes: “classic” “intermittent”, “mild”, Thiamine responsive, and E3-deficient with lactic acidosis. Classification of subtypes according to nature of gene mutation by genetic complementation analysis after somatic cell hybridisation (1980) Classic MSUD is the most severe and most common form Maple Syrup Urine Disease (MSUD)By Jenny Morrison (836445)

  2. Symptoms – “classic” MSUD 4 of the MSUD clinical subtypes • Onset in the first week of life: • Maple syrup odour (in urine and on body) • Feeding difficulties and vomiting • Shrill cry • Hypertonicity (episodes alternate with flaccidity) • No Moro reflex and suppressed deep tendon reflexes • Frequent convulsions • Survivors suffer from severe mental retardation & motor development retardation (Bondy & Rosenberg, 1980)

  3. Inheritance • Autosomal recessive • Frequency: • 1 in 185,000 newborns world wide (Chuang et al, 1995) • 1 in 176 newborns in the Mennonite population of Lancaster, Pennsylvania (due to consanguinity) • Panethnic distribution Genetic Counselling • Relatives of the affected individual have high genetic risks (1 in 4) • Extremely low risks to offsprings of healthy sibs or more distant relatives

  4. Molecular genetics of the BCKAD • each molecular phenotype can have > 1 clinical phenotype as different mutations in the same subunit may have different effects on the stability and function of the polypeptide. • MSUD type II constitute the majority of mutations reported

  5. MSUD Type IA E1α mRNA sequence 1 gccggaccgc tgagtggttg ttagccaaga tggcggtagc gatcgctgca gcgagggtct 61 ggcggctaaa ccgtggtttg agccaggctg ccctcctgct gctgcggcag cctggggctc 121 ggggactggc tagatctcac ccccccaggc agcagcagca gttttcatct ctggatgaca 181 agccccagtt cccaggggcc tcggcggagt ttatagataa gttggaattc atccagccca 241 acgtcatctc tggaatcccc atctaccgcg tcatggaccg gcaaggccag atcatcaacc 301 ccagcgagga cccccacctg ccgaaggaga aggtgctgaa gctctacaag agcatgacac 361tgcttaacac catggaccgc atcctctatg agtctcagcg gcagggccgg atctccttct 421acatgaccaa ctatggtgag gagggcacgc acgtggggag tgccgccgcc ctggacaaca 481 cggacctggt gtttggccag taccgggagg caggtgtgct gatgtatcgg gactaccccc 541tggaactatt catggcccag tgctatggca acatcagtga cttgggcaag gggcgccaga 601tgcctgtcca ctacggctgc aaggaacgcc acttcgtcac tatctcctct ccactggcca 661cgcagatccc tcaggcggtg ggggcggcgt acgcagccaa gcgggccaat gccaacaggg 721tcgtcatctg ttacttcggc gagggggcag ccagtgaggg ggacgcccat gccggcttca 781acttcgctgc cacacttgag tgccccatca tcttcttctg ccggaacaat ggctacgcca 841tctccacgcc cacctctgag cagtatcgcg gcgatggcat tgcagcacga ggccccgggt 901atggcatcat gtcaatccgc gtggatggta atgatgtgtt tgccgtatac aacgccacaa 961aggaggcccg acggcgggct gtggcagaga accagccctt cctcatcgag gccatgacct 1021acaggatcgg gcaccacagc accagtgacg acagttcagc gtaccgctcg gtggatgagg 1081tcaattactg ggataaacag gaccacccca tctcccggct gcggcactat ctgctgagcc 1141aaggctggtg ggatgaggag caggagaagg cctggaggaa gcagtcccgc aggaaggtga 1201tggaggcctt tgagcaggcc gagcggaagc ccaaacccaa ccccaaccta ctcttctcag 1261acgtgtatca ggagatgccc gcccagctcc gcaagcagca ggagtctctg gcccgccacc 1321tgcagaccta cggggagcac tacccactgg atcacttcga taagtgagac ctgctcagcc 1381cacccccacc catcctcagc taccccgaga ggtagcccca ctctaagggg agcaggggga 1441cctgacagca caccactgtc ttccccagtc agctccctct aaaatactca gcggccaggg 1501cggctgccac tcttcacccc tgctcctccc ggctgttaca ttgtcagggg acagcatctg 1561cagcagttgc tgaggctccg tcagccccct cttcacctgt tgttacagtg ccttctccca 1621ggggctgggt gagggcacat tcaggactag aagcccctct gggcatgggg tggacatggc 1681aggtcagcct gtggaacttg cgcaggtgcg agtggccagc agaggtcacg aataaactgc 1741atctctgcgc ctggctctct accaaaaaaa aaaaaaaaaa a Protein Sequence MAVAIAAARVWRLNRGLSQAALLLLRQPGARGLARSHPPRQQQQFSSLDDKPQFPGASAEFIDKLEFIQPNVISGIPIYRVMDRQGQIINPSEDPHLPKEKVLKLYKSMTLLNTMDRILYESQRQGRISFYMTNYGEEGTHVGSAAALDNTDLVFGQYREAGVLMYRDYPLELFMAQCYGNISDLGKGRQMPVHYGCKERHFVTISSPLATQIPQAVGAAYAAKRANANRVVICYFGEGAASEGDAHAGFNFAATLECPIIFFCRNNGYAISTPTSEQYRGDGIAARGPGYGIMSIRVDGNDVFAVYNATKEARRRAVAENQPFLIEAMTYRIGHHSTSDDSSAYRSVDEVNYWDKQDHPISRLRHYLLSQGWWDEEQEKAWRKQSRRKVMEAFEQAERKPKPNPNLLFSDVYQEMPAQLRKQQESLARHLQTYGEHYPLDHFDK

  6. MSUD Type IB E1β mRNA transcript variant 2 1 aggcggcgtg cggctgcata gcctgagaat cccggtggtg agcggggatg gcggttgtag 61 cggcggctgc cggctggcta ctcaggctca gggcggcagg ggctgagggg cactggcgtc 121 ggcttcctgg cgcggggctg gcgcggggct ttttgcaccc cgccgcgact gtcgaggatg 181 cggcccagag gcggcaggtg gctcatttta ctttccagcc agatccggag ccccgggagt 241 acgggcaaac tcagaaaatg aatcttttcc agtctgtaac aagtgccttg gataactcat 301 tggccaaaga tcctactgca gtaatatttg gtgaagatgt tgcctttggt ggagtcttta 361 gatgcactgt tggcttgcga gacaaatatg gaaaagatag agtttttaat accccattgt 421 gtgaacaagg aattgttgga tttggaatcg gaattgcggt cactggagct actgccattg 481 cggaaattca gtttgcagat tatattttcc ctgcatttga tcagattgtt aatgaagctg 541 ccaagtatcg ctatcgctct ggggatcttt ttaactgtgg aagcctcact atccggtccc 601 cttggggctg tgttggtcat ggggctctct atcattctca gagtcctgaa gcattttttg 661 cccattgccc aggaatcaag gtggttatac ccagaagccc tttccaggcc aaaggacttc 721 ttttgtcatg catagaggat aaaaatcctt gtatattttt tgaacctaaa atactttaca 781 gggcagcagc ggaagaagtc cctatagaac catacaacat cccactgtcc caggccgaag 841 tcatacagga agggagtgat gttactctag ttgcctgggg cactcaggtt catgtgatcc 901 gagaggtagc ttccatggca aaagaaaagc ttggagtgtc ttgtgaagtc attgatctga 961 ggactataat accttgggat gtggacacaa tttgtaagtc tgtgatcaaa acagggcgac 1021 tgctaatcag tcacgaggct cccttgacag gcggctttgc atcggaaatc agctctacag 1081 ttcaggagga atgtttcttg aacctagagg ctcctatatc aagagtatgt ggttatgaca 1141 caccatttcc tcacattttt gaaccattct acatcccaga caaatggaag tgttatgatg 1201 cccttcgaaa aatgatcaac tattgaccat atagaaaagc tggaagatta tgactagata 1261 tggaaatatt ttttctgaat ttttttttat atttcctccg acttacctct ttttgaaaag 1321 agagttttta ttaaatgaac catcatgata ttggctgaaa agttctacat tctattattg 1381 tattgtaaca cacatgtatt gatgattttc attaagagtt tcagattaac tttgaaaaat 1441 attccacatg gtaatcttat aaattctgtt taattacatc tgtaaatatt atgtgtgtga 1501 tagtattcaa taaagtaaaa tcaaattgtc aaaaaaaaaa aaaaaaaaaa aa// Protein sequence MAVVAAAAGWLLRLRAAGAEGHWRRLPGAGLARGFLHPAATVEDAAQRRQVAHFTFQPDPEPREYGQTQKMNLFQSVTSALDNSLAKDPTAVIFGEDVAFGGVFRCTVGLRDKYGKDRVFNTPLCEQGIVGFGIGIAVTGATAIAEIQFADYIFPAFDQIVNEAAKYRYRSGDLFNCGSLTIRSPWGCVGHGALYHSQSPEAFFAHCPGIKVVIPRSPFQAKGLLLSCIEDKNPCIFFEPKILYRAAAEEVPIEPYNIPLSQAEVIQEGSDVTLVAWGTQVHVIREVASMAKEKLGVSCEVIDLRTIIPWDVDTICKSVIKTGRLLISHEAPLTGGFASEISSTVQEECFLNLEAPISRVCGYDTPFPHIFEPFYIPDKWKCYDALRKMINY Alternate splicing results in 2 transcripts that encode the same protein

  7. MSUD Type IB cont. 1921 cccagctaat tttttatatt tttagtagag acggggtttc accatgttgg ccaggatggt 1981 ctcgatctct tgaccttgtg ttccacccgt cttggcctcc caaagcgctg gaattacagg 2041 catgagccac cgcgcctggc ctgtatatgt gatttctaaa aaatagatgc atgcatatgt 2101 taacattgaa tagtcaatca ctagatgaag atgctctcta ccatggttta gattgcaagt 2161 gtactttata ccattgtttc aacttcaacc tttatttttg tatatatttt ttcaactact 2221 taaactgttc atgaataggc gtactttctg tatttaaaaa tggcccctca agcaccgtta 2281 atttacattc cagttattta catgataatt catgacattc tgaaacttgc ctgtatatta 2341 tctgaaaaat ggatttcttg aggaaaagat ctgtttattg tatgtaagga aaaattttac 2401 ctgaaaacaa acaaacaaac cctaaaactc agcaccacta ccatttccag aagctttttt 2461 agcaagtgaa tattttttac ataatggata ataaatggta tttattcatc atgattttct 2521 aagtaatgct tatcagcccc ttcagtggtg ttattctaac aaaatgaata cattacaaat 2581 tattaagtta gcttttcaga gttttaatat agaagttact agcactgaca cactgatttt 2641 gaaatgtttc aaaatgagta gatacgatta gatcctttac cttttaatat ctagtttttc 2701 caaaaatgat agtaatatct tttgaagaac tatgcttttt caaaagcaaa atcaactctg 2761 tataatagca cattctctac tttttaaaga tcagaaatgc tagaattctt gacttttgtg 2821 tatgggtagt aaatctagct cactgaaaat cagagtgaaa cgcctttaca tttgtgcgga 2881 tagagaagtt aactctccct catatgtcac tgtgctacca taatccctac attttctgtc 2941 tgttctagtc taagaatatt gttatagatg gaagttagga ccattagccc acagatgcgt 3001 gtattctctc agacataccg gtgtagatgc catatttctg atgtcttctt aatgtctgtg 3061 aaagcaactg gcatctacaa taaatcacac ttagaactgg ttagaggact ccctcacttt 3121 tgttgtccat gtggttccct tccgtggacc agccgtaata aagagccaag gtagtgatgg 3181 tggccacgtg cctcgttgct atttttaaag taatattcag atgtggtttt aaatttagat 3241 tatgtattcc ttttgaaaca taagaaaaac atttaaacct atgctgaaaa tacgataaaa 3301 gaaaaacaac tccaatatgc taaaagttaa atatggtatt taagaaaata gtcatgtatg 3361 caattgagaa agtctataat ttattttaca gaaaagctgg aagattatga ctagatatgg 3421 aaatattttt tctgaatttt tttttatatt tcctccgact tacctctttt tgaaaagaga 3481 gtttttatta aatgaaccat catgatattg gctgaaaagt tctacattct attattgtat 3541 tgtaacacac atgtattgat gattttcatt aagagtttca gattaacttt gaaaaatatt 3601 ccacatggta atcttataaa ttctgtttaa ttacatctgt aaatattatg tgtgtgatag 3661 tattcaataa agtaaaatca aattgtcaaa aaaaaaaaaa aaa mRNA transcript variant 1 1 aggcggcgtg cggctgcata gcctgagaat cccggtggtg agcggggatg gcggttgtag 61 cggcggctgc cggctggcta ctcaggctca gggcggcagg ggctgagggg cactggcgtc 121 ggcttcctgg cgcggggctg gcgcggggct ttttgcaccc cgccgcgact gtcgaggatg 181 cggcccagag gcggcaggtg gctcatttta ctttccagcc agatccggag ccccgggagt 241 acgggcaaac tcagaaaatg aatcttttcc agtctgtaac aagtgccttg gataactcat 301 tggccaaaga tcctactgca gtaatatttg gtgaagatgt tgcctttggt ggagtcttta 361 gatgcactgt tggcttgcga gacaaatatg gaaaagatag agtttttaat accccattgt 421 gtgaacaagg aattgttgga tttggaatcg gaattgcggt cactggagct actgccattg 481 cggaaattca gtttgcagat tatattttcc ctgcatttga tcagattgtt aatgaagctg 541 ccaagtatcg ctatcgctct ggggatcttt ttaactgtgg aagcctcact atccggtccc 601 cttggggctg tgttggtcat ggggctctct atcattctca gagtcctgaa gcattttttg 661 cccattgccc aggaatcaag gtggttatac ccagaagccc tttccaggcc aaaggacttc 721 ttttgtcatg catagaggat aaaaatcctt gtatattttt tgaacctaaa atactttaca 781 gggcagcagc ggaagaagtc cctatagaac catacaacat cccactgtcc caggccgaag 841 tcatacagga agggagtgat gttactctag ttgcctgggg cactcaggtt catgtgatcc 901 gagaggtagc ttccatggca aaagaaaagc ttggagtgtc ttgtgaagtc attgatctga 961 ggactataat accttgggat gtggacacaa tttgtaagtc tgtgatcaaa acagggcgac 1021 tgctaatcag tcacgaggct cccttgacag gcggctttgc atcggaaatc agctctacag 1081 ttcaggagga atgtttcttg aacctagagg ctcctatatc aagagtatgt ggttatgaca 1141 caccatttcc tcacattttt gaaccattct acatcccaga caaatggaag tgttatgatg 1201 cccttcgaaa aatgatcaac tattgaccat ataggtaggt atgcatcttg agaaagctac 1261 tatgtgcccc tgacattaac gtactgttaa ccaagacaca gcaatcatca gtgttttgat 1321 ggtaacaaac tttgatggta aagttgataa aaggcaactt tcagaagaaa ataatgtgct 1381 ttagaaaaaa aattcaaatt tatagtagta tatttacatt tttgttgttg ttgttctgag 1441 atggagtctc actctgtcgc ccaggctaga ctgcagtggt gcaatctcag ctcactgcaa 1501 cctcccccct acccccgagt tcaagcaatt ctcctgcctc agcctgctga gtagttggga 1561 ttacaggtgc ccaccaccat gcccagctaa tttttgtgtt tttattggag gtggggtttc 1621 actatgttgg ctcagctgat ttcaaattcc tgacctcaag tgatccacct gccttagcct 1681 cccaaagtgc tgggattaca ggcatgagcc actgcacctg gctatattta catttaatag 1741 aaacatatct agcatatgta tatgtgattt tttttttttt tgagaccgag tctcactctg 1801 tcaccaggct ggagtgcagt ggtgcgatct tggctcatgg caacctccgc ctcccaggtt 1861 caagcgattg tcctgcctca gtctcctgag tagctgggac tacaggtgtg caccaacatg

  8. MSUD Type II E2 mRNA sequence 1 atttccgggg taagatggct gcagtccgta tgctgagaac ctggagcagg aatgcgggga 61 agctgatttg tgttcgctat tttcaaacat gtggtaatgt tcatgttttg aagccaaatt 121 atgtgtgttt ctttggttat ccttcattca agtatagtca tccacatcac ttcctgaaaa 181 caactgctgc tctccgtgga caggttgttc agttcaagct ctcagacatt ggagaaggga 241 ttagagaagt aactgttaaa gaatggtatg taaaagaagg agatacagtg tctcagtttg 301 atagcatctg tgaagttcaa agtgataaag cttctgttac catcactagt cgttatgatg 361 gagtcattaa aaaactctat tataatctag acgatattgc ctatgtgggg aagccattag 421 tagacataga aacggaagct ttaaaagatt cagaagaaga tgttgttgaa actcctgcag 481 tgtctcatga tgaacataca caccaagaga taaagggccg aaaaacactg gcaactcctg 541 cagttcgccg tctggcaatg gaaaacaata ttaagctgag tgaagttgtt ggctcaggaa 601 aagatggcag aatacttaaa gaagatatcc tcaactattt ggaaaagcag acaggagcta 661 tattgcctcc ttcacccaaa gttgaaatta tgccacctcc accaaagcca aaagacatga 721 ctgttcctat actagtatca aaacctccgg tattcacagg caaagacaaa acagaaccca 781 taaaaggctt tcaaaaagca atggtcaaga ctatgtctgc agccctgaag atacctcatt 841 ttggttattg tgatgagatt gaccttactg aactggttaa gctccgagaa gaattaaaac 901 ccattgcatt tgctcgtgga attaaactct cctttatgcc tttcttctta aaggctgctt 961 ccttgggatt actacagttt cctatcctta acgcttctgt ggatgaaaac tgccagaata 1021 taacatataa ggcttctcat aacattggga tagcaatgga tactgagcag ggtttgattg 1081 tccctaatgt gaaaaatgtt cagatctgct ctatatttga catcgccact gaactgaacc 1141 gcctccagaa attgggctct gtgggtcagc tcagcaccac tgatcttaca ggaggaacat 1201 ttactctttc caacattgga tcaattggtg gtacctttgc caaaccagtg ataatgccac 1261 ctgaagtagc cattggggcc cttggatcaa ttaaggccat tccccgattt aaccagaaag 1321 gagaagtata taaggcacag ataatgaatg tgagctggtc agctgatcac agagttattg 1381 atggtgctac aatgtcacgc ttctccaatt tgtggaaatc ctatttagaa aacccagctt 1441 ttatgctact agatctgaaa tgaagactga taagacattc ttgaactttt tgagcttcca 1501 aagagtatgt aaaccctagc tgtgccagca catgttcatc tttacaattt atattgtaaa 1561 cgatttgtat cgtatgatta aggatctaag gcacaatatt tgtcactgtt ctattagact 1621 ttttactgaa aatgaataat ggtgtaatgg ttctcctggg gctgtcacat tttataggtc 1681 agagtgtgac ttcttaatat ggtgctgatg tttttgtgtc aatggcttga aactggcaag 1741 attaacaaaa ttaggccggg catggtggct cacgcctgta atccagcact ttgggaggcc 1801 caggtggggc gatcacctga ggttagaagt ttgagaccag cctggccaac atggtgaaac 1861 ctggcctcta cctaaaaaat acaaaattga ccgggtgtgg tggtgggtac cgctacttgg 1921 gaggctgagg caggagaatc gcttgaacct gggaggtgga ggttgcagtg agctgagatc 1981 gtgctattgc actccagcct gggcgacaga gcaagacgcc atctcaaaaa caaaaaaaac 2041 aaaattcatg ttactaaaag acaggtagcc atatacagac agtatatgcc ctattttttt 2101 taactgactc ttaatgaaac tttaatttta cttaattaag aaatggaatt tatatacaaa 2161 aatattttcc atttccgtta ttatgctaat tgttgtatga aataagtgca attatacttc 2221 tcttttgaga tatccaagag tatattcttg ctctgtatag agaatatcat ctgatagtgt 2281 cttatttata ttaattaatg tctttgaaaa gggaaaagta taaactggcc ttaaaattgt 2341 ccaattatag ttttataacc agtctattaa aggtgtttgt ttaaaatgga tatagtttta 2401 gatttgtggt aatgctttgg tattttcttg gggaagacct tcacctttgc aaacttccct 2461 catgtaagga aggtacttta aatgtagcag ccactgacat ttcttttttt aaaaaaaatt 2521 tgagaagtct acttcctttt aacttttttg gtcttcagct aaaaaatagg ataagaaatt 2581 aaggtctatt ccattctcca tatcctgggt aagaatgtaa ataagaggag aaggaagagt 2641 ctaatagtaa ttatggatat aaaaaataag aaattttgta tagaaatgaa ggtttcataa 2701 tgatcatttt gttaaaggtc tactttaatc agaaatagca acgagatgaa tgtatccaac 2761 atttcaattt gcattcggaa atccatgttg tttctaatat tgtccagttg aaaactgtat 2821 gccaaaatta gttgtttaag tgaagttttg tgacagaaaa aaggttgttt taatatctac 2881 ttggtttttc tcaaaatgga aataatttta aaatcaggaa agaataaatc agccaggtgt 2941 gatgacttgt aactgtaatc ccagttatag gggaggctga agcaggagga tcacttgagg 3001 ccaggagttt gagaccagcc tgggcaacat agtgagatcc catctcaaaa aacattattt 3061 ttaaaattag cctggtggct cacgcctgta atcccagcac tttgggaggc cgaggtggcc 3121 agatcacctg aggtcaggag ttcgagacca ccctggccaa catggtgaaa ccccatctct 3181 acagttttgt aaaaatacaa aaattacctg ggcctggtgc acaggcctgt agtcccagct 3241 acttgggagg ctgaggcagg agaattgctt gagcccaaga ggtggaggtt acagtgagca 3301 gagatcacac cactgcactc cagcctgggt ggcagagcaa cacttcgtct cagaaaaaaa 3361 aaaaaaaacc aaaaaccaaa aagccaagtg tggtggtgtg cacctatagt cccagctact 3421 caggaagctg agacaagagg atcaattgag cccaggagtt caaagctgta gtgagctgtc 3481 attgtgccac tatcctccag tatgggtgac agagtgagac ctggtctcta aaaat Protein sequence MAAVRMLRTWSRNAGKLICVRYFQTCGNVHVLKPNYVCFFGYPSFKYSHPHHFLKTTAALRGQVVQFKLSDIGEGIREVTVKEWYVKEGDTVSQFDSICEVQSDKASVTITSRYDGVIKKLYYNLDDIAYVGKPLVDIETEALKDSEEDVVETPAVSHDEHTHQEIKGRKTLATPAVRRLAMENNIKLSEVVGSGKDGRILKEDILNYLEKQTGAILPPSPKVEIMPPPPKPKDMTVPILVSKPPVFTGKDKTEPIKGFQKAMVKTMSAALKIPHFGYCDEIDLTELVKLREELKPIAFARGIKLSFMPFFLKAASLGLLQFPILNASVDENCQNITYKASHNIGIAMDTEQGLIVPNVKNVQICSIFDIATELNRLQKLGSVGQLSTTDLTGGTFTLSNIGSIGGTFAKPVIMPPEVAIGALGSIKAIPRFNQKGEVYKAQIMNVSWSADHRVIDGATMSRFSNLWKSYLENPAFMLLDLK

  9. MSUD Type II - Mutations

  10. MSUD Type III E3 mRNA sequence 1 gcgcagggag gggagacctt ggcggacggc ggagccccag cggaggtgaa agtattggcg 61 gaaaggaaaa tacagcggaa aaatgcagag ctggagtcgt gtgtactgct ccttggccaa 121 gagaggccat ttcaatcgaa tatctcatgg cctacaggga ctttctgcag tgcctctgag 181 aacttacgca gatcagccga ttgatgctga tgtaacagtt ataggttctg gtcctggagg 241 atatgttgct gctattaaag ctgcccagtt aggcttcaag acagtctgca ttgagaaaaa 301 tgaaacactt ggtggaacat gcttgaatgt tggttgtatt ccttctaagg ctttattgaa 361 caactctcat tattaccata tggcccatgg aacagatttt gcatctagag gaattgaaat 421 gtccgaagtt cgcttgaatt tagacaagat gatggagcag aagagtactg cagtaaaagc 481 tttaacaggt ggaattgccc acttattcaa acagaataag gttgttcatg tcaatggata 541 tggaaagata actggcaaaa atcaagtcac tgctacgaaa gctgatggcg gcactcaggt 601 tattgataca aagaacattc ttatagccac gggttcagaa gttactcctt ttcctggaat 661 cacgatagat gaagatacaa tagtgtcatc tacaggtgct ttatctttaa aaaaagttcc 721 agaaaagatg gttgttattg gtgcaggagt aataggtgta gaattgggtt cagtttggca 781 aagacttggt gcagatgtga cagcagttga atttttaggt catgtaggtg gagttggaat 841 tgatatggag atatctaaaa actttcaacg catccttcaa aaacaggggt ttaaatttaa 901 attgaataca aaggttactg gtgctaccaa gaagtcagat ggaaaaattg atgtttctat 961 tgaagctgct tctggtggta aagctgaagt tatcacttgt gatgtactct tggtttgcat 1021 tggccgacga ccctttacta agaatttggg actagaagag ctgggaattg aactagatcc 1081 tagaggtaga attccagtca ataccagatt tcaaactaaa attccaaata tctatgccat 1141 tggtgatgta gttgctggtc caatgctggc tcacaaagca gaggatgaag gcattatctg 1201 tgttgaagga atggctggtg gtgctgtgca cattgactac aattgtgtgc catcagtgat 1261 ttacacacac cctgaagttg cttgggttgg caaatcagaa gagcagttga aagaagaggg 1321 tattgagtac aaagttggga aattcccatt tgctgctaac agcagagcta agacaaatgc 1381 tgacacagat ggcatggtga agatccttgg gcagaaatcg acagacagag tactgggagc 1441 acatattctt ggaccaggtg ctggagaaat ggtaaatgaa gctgctcttg ctttggaata 1501 tggagcatcc tgtgaagata tagctagagt ctgtcatgca catccgacct tatcagaagc 1561 ttttagagaa gcaaatcttg ctgcgtcatt tggcaaatca atcaactttt gaattagaag 1621 attatatatt tttttttctg aaatttcctg ggagcttttg tagaagtcac attcctgaac 1681 aggatattct cacagctcca agaatttcta ggactgaatt atgaaacttt tggaaggtat 1741 ttaataggtt tggacaaaat ggaatactct tatatctata ttttacataa atttagtatt 1801 ttgtttcagt gcactaatat gtaagacaaa aaggactact tattgtagtc atcctggaat 1861 atctccgtca actcatattt tcatgctgtt catgaaagat tcaatgcccc tgaatttaaa 1921 tagctctttt ctctgataca gaaaagttga attttacatg gctggagcta gaatttgata 1981 tgtgaacagt tgtgtttgaa gcacagtgat caagttattt ttaatttggt tttcacattg 2041 gaaacaagtc agtcattcag atatgattca aatgtctata aaccaaactg atgtaagtaa 2101 atggtctctc acttgtttta tttaacctct aaattctttc attttagggg tagcatttgt 2161 gttgaagagg ttttaaagct tccattgttg tctgcaactc tgaagggtaa ttatatagtt 2221 acccaaatta agagagtcta tttacggaac tcaaatacgt gggcattcaa atgtattaca 2281 gtggggaatg aagatactga aataaacgtc ttaaatattc Protein Sequence MQSWSRVYCS LAKRGHFNRI SHGLQGLSAV PLRTYADQPI DADVTVIGSG PGGYVAAIKA AQLGFKTVCI EKNETLGGTC LNVGCIPSKA LLNNSHYYHM AHGTDFASRG IEMSEVRLNL DKMMEQKSTA VKALTGGIAH LFKQNKVVHV NGYGKITGKN QVTATKADGG TQVIDTKNIL IATGSEVTPF PGITIDEDTI VSSTGALSLK KVPEKMVVIG AGVIGVELGS VWQRLGADVT AVEFLGHVGG VGIDMEISKN FQRILQKQGF KFKLNTKVTG ATKKSDGKID VSIEAASGGK AEVITCDVLL VCIGRRPFTK NLGLEELGIE LDPRGRIPVN TRFQTKIPNI YAIGDVVAGP MLAHKAEDEG IICVEGMAGG AVHIDYNCVP SVIYTHPEVA WVGKSEEQLK EEGIEYKVGK FPFAANSRAK TNADTDGMVK ILGQKSTDRV LGAHILGPGA GEMVNEAALA LEYGASCEDI ARVCHAHPTL SEAFREANLA ASFGKSINF

  11. Metabolic functions • Branched chain dehydrogenase complex (BCKAD) • 3 catalytic components: branched-chain alpha-keto acid decarboxylase (E1), lipoamide acyltransferase (E2) and lipoamide dehydrogenase (E3) • 2 regulatory enzymes: kinase and phosphotase • Encoded by 6 genetic loci • Mutation in any of the loci can result in defect • Defect in BCKAD causes a block in BCKA oxidative decarboxylation • Accumulation of BCKA (1) transamination by BCAA amino transferase (2) oxidative decarboxylation by BCKAD (3) dehydrogenation by isovaleryl-CoA dehydrogenase (4) dehydrogenation by alpha-methyl branched chain cyl-CoA dehydrogenase (Chuang & Shih, 1995)

  12. Screening and Diagnosis • Prenatal diagnosis • analysis of cultured amniocytes obtained at mid-trimester amniocentesis • direct analysis of tissues or cultured cells from chorionic villi sample taken during first trimester • Use allele-specific oligonucleotide (ASO) probe following PCR to detect mutation in DNA obtained from amniocytes • Attempts at measuring amniotic fluid concentration of BCAA, BCKA and α-hydroxyacids have been unsuccessful • Routine newborn screening • Guthrie bacterial inhibition assay Increase leucine levels in blood spots Detect classic, intermediate and E3-deficient MSUD but intermediate may be missed due to lower leucine levels than classic • Tandem mass spectroscopy coupled with fast atom bombardment (FAB) ionisation Detect organic acids and amino acids abnormalities in blood and urine samples on filter paper

  13. Screening and Diagnosis cont. • General diagnosis or genetic studies • Urine 2,4-dinitrophenylhydrazine (DNPH) test • Gas chromatographic mass spectroscopy (GC-MS) • Enzymic studies of cell cultures (skin fibroblasts and lymphoblasts) • Allele-specific oligonucleotide (ASO) probing Historical perspective • Diagnosis relied on the recognition of clinical symptoms and signs and Chemical and enzymological analysis were performed if indicated (Galjaard 1980)

  14. Therapies and Management History of dietary therapies Dietary therapies started in 1959. Gelatin has low BCAA and was used as a source of BCAA in England in the early days. A synthetic formula was developed by Snyderman et al in the United States which consisted of 18 amino acids (based on breastmilk composition) carbohydrates, fat, minerals and vitamins. Based on this formula, other commercial medical diets have since been created. Long term dietary management • Restrict intake of BCAA in diet to the amount essential for growth • Start as soon as possible and continue for life • Treat classic and intermediate MSUD patients the same way • For intermittent MSUD, decrease protein intake during episodes • Monitor plasma BCAA levels weekly for the first 6 months and keep as close to normal as possible • A trial of thiamine therapy is recommended to determine thiamine responsiveness in all new patients

  15. Therapies and Management cont. Acute-phase management • Infection and stress can cause a significant accumulation of BCAA and BCKA which can be life threatening • Treatment involves: • Rapid removal of toxic metabolites Exchange transfusion (early 1960’s) achieved limited success Peritoneal dialysis (1969) produced significant improvement within hours. It is simple to implement and has become an established procedure for treating patients in crisis Hemodialysis is equally successful but requires specialised equipment and personnel Continuous arteriovenous hemoperfusion can be used for adults but hastechnical limitations when applied to newborns • Parenteral Nutritional therapy BCAA-free L-amino acid mixture combined with glucose, lipid, electrolytes and vitamins • Minimise catabolic state and/or promote anabolism use insulin and carbohydrate to promote anabolism

  16. Therapies and Management cont. Key References • Other therapies • Introducing subunits of BCKDH enzyme into cells using a retrovirous • Liver transplant • Somatic gene therapy • Bondy, P.K. & Rosenberg, L.C. 1980, Metabolic Control and Disease, 8th Edition, W.B. Saunders Company, Philadelphia • Galjaard, H. 1980, Genetic Metabolic Diseases: Early Diagnosis and Prenatal Analysis, Elsevier/North-Holland Biomedical Press, Amsterdam • Chuang, D.T. & Shih, V.E. 1995, ‘Disorders of Branched Chain Amino Acid and Keto Acid Metabolism’, in The Metabolic and Molecular Bases of Inherited Diseases, vol. 1,7th Edition, eds Scriver et al., McGraw-Hill, New York • OMIM, URL: http://www3.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=248600 • Ensemble, URL: http://www.ensembl.org/homo_sapians/genereview?gene=ENSG00000137992 (ENSG00000142046, ENSG00000083123, ENSG00000091140)