Introduction to Introduction to biochemical genetics

Case 3- MPS Ihttp://eyepathologist.com/images/KL1771.jpghttp://deti.msk.ru/plaxin_egor.jpghttp://myweb.lsbu.ac.uk/dirt/museum/margaret/438-1811-2640151.jpgCase 4-cystinuriahttp://www.nature.com/ki/journal/v73/n8/images/5002790f1.jpghttp://graphics8.nytimes.com/images/2007/08/01/health/adam/17046.jpg

History of biochemicalgenetics1857-1936http://www.historiadelamedicina.org/imagenes/garrod.jpg

Trophîme Bigot, 16.-17.stoletíhttp://www.thetoque.com/010605/pics/urine.jpghttp://images.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Bigot,_Trophime_-_A_Doctor_Examining_Urine.jpg/• 1857 L.Pasteur demonstrates microbial origin offermentation, R.Wirchow describes mitosis• 1867 dynamit• 1874 jeans• 1886 automobil=car• 1890 underground• 1895 cinematograf• 1902 periskop, el.typewriter; Nobel prize fordiscovery of malaria transmission• 1908 Nobel prize for discovery of immunity• 1936 tape recored; Nobel prize forneurotransmitter research

Lancet, vol ii, 1902, 1616-1620

Expansion of the field1908• 5 diseases(alkaptonuria,cystinuria, porphyria,pentosuria, congenitalsteatorhea)•1909 first textbook•incidence unknown•dx: 4 metabolites inurine•Rx nonecca 1960• ca 40-50diseases•analyticalmethods•incidence of PKU•PKU- 1stscreening program(R.Guthrie)•PKU-1st treatableIEM (H.Bickel)2009•at least 500 diseases•Medline 122.797papers (28/9/2009)•textbook-web tb bbased•incidence at least1:1.000•Dx: metabolites,enzymes, DNA•screening MS-MS•Rx for ~ 1/3 diseasesBiochemical genetics in the ČR• PKU screening 1975-Doc.Blehová, Prof.Hyánek,Ing.Mrskoš• Dx of other IEMs-leader Prof.Hyánek• labs in Prague, H.Králové, Brno, Olomouc,Ostrava• in 2009: selective screening ~ 100 pacientů/rok (incidence1:1000) newborn screening- 10 IEMs since October 1 2009,expected incidence 1:4000

First IEM:Alkaptonuriahttp://bjo.bmj.com/content/vol83/issue6/images/large/98532.f1.jpeghttp://www.scielo.br/img/revistas/rbr/v46n5/a14fig02.jpghttp://www.mja.com.au/public/issues/184_12_190606/sha20286_fm-1b.jpg

1859 Boedeker- alkapton in urine1891 alkapton=homogentisic acid

http://www.bioinformatics.nl/webportal/background/images/mendelexperiment.gifGarrodův revolutionary concept• Chemical individuality is determined bygenes• Inborn errors of metabolism= disturbanceof chemical individuality

Alkaptonuria in 2009• retrospective reasearch ofmummy HARWA 1500 př.n.l.• pateints known before Garrod• 1902 Garrod• 1909 tyrosine degradationpathway described• 1958 enzyme defect inalkaptonuria established• 1996 HGO gene description• 2003 treatment with nitisoneCoxarthrosisValvularinvolvementUrolithiasishttp://bjo.bmj.com/content/vol83/issue6/images/large/98532.f1.jpeghttp://www.scielo.br/img/revistas/rbr/v46n5/a14fig02.jpghttp://www.mja.com.au/public/issues/184_12_190606/sha20286_fm-1b.jpg

http://www.natuurlijkerwijs.com/english/b4f4ca00.gif• Liver HGOdeficiency• Incidence 1:250000 až 1:11 000 000• High incidenceSlovakia• Late complicationsfrequent• Rx inefficienthttp://ourworld.compuserve.com/homepages/sbrillanti/liver2.jpg

http://en.wikipedia.org/wiki/Novel treatment in alkaptonurianitison (NTBC)http://www.natuurlijkerwijs.com/english/b4f4ca00.gif

Genetic origin of IEMs

Genetic origin of IEM• Monogenic Mendelian inheritance AR inheritance GR/GD inheritance rarely AD inheritanceX• Mitochondrial inheritance• Epigenetic changes• X-inactivation• Epsistasis• Gene x environment interaction• otherCommon types of mutations

Molecular consequences of mutations• Protein amounts decreased same increased• Protein properties changes of isolated functions global changes misfolding• Nonprotein gene products siRNARole of mutations in evolution• Source of variability(less important thanmeiotic recombinationand combination ofgametes)• Favourable mutationsare rare and alreadycontained in genomes• Genetic diseases= tip of• Genetic diseases tip oficeberg (of geneticvariability)

Mutations affect different domains• e.g. PAH• cytosolic enzyme• homotetramer• BH4 as cofaktor• complicatedmechanism ofcatalysisErlandsen H and Stevens RC, The Structural Basis of Phenylketonuria. Mol Genet Metab. 1999 Oct; 68(2):103-125.Cellular consequences ofmutations (e.g.CFTR)http://student.biology.arizona.edu/honors97/group7/Hallick1.gif

Genotype-phenotype (M.Gaucher)Phenotypeseveresplenomegalyanemiabone disorderCNSmildsplenomegalyanemiaunclearhttp://www.nature.com/embor/journal/v4/n7/thumbs/embor873-f4.gifHealth-disease thresholdclinical manifestationenvironmentgenespreclinical testgenetic test

IEM treatment- modifying environmentclinical manifestationenvironmentgenespreclinical testgenetic testGene x environment interaction (PKU)http://www.pkunews.org/adults/image005.gif

Disease modification byenvironment (alpha1-antitrypsin)Current genetics is notMendelianclassical genetics1 gene=1 disease• 1 gene = more diseases• 1 gene = diseases withdifferent types of inheritance• several genes = same disease• digenic inheritance• transgenerationaltransmission of epigeneticmarks• other ……

Genetics has been and will be full of suprisesPatophysiologicalmechanisms in IEMs

PatophysiologyprecursorsubstratebyproductenzymetransporterproductPatophysiologyprecursorsubstratebyproductExamples:• Phe a Phe-derivatives• ammonia• cystine in cystinosis• cystine in cystinuria• mucopolysaccharides

PatophysiologyExamples:• glucose in GSD• ketone bodies in betaoxidationdefects• plasmalogens inperoxisom.diseases• cysteine in CBS deficiency• AdoMet in RM• ATP in mitochondrialdiseasesproductLocal vs. systemic consequencesLocal consequence, e.g.:• MPS-bones, tendons, spleen, liver,CNS• cystinuria-urinary urinary tract

Local vs. systemic consequencesDistant consequences-e.g.• urea cycle disorders- coma• organic acidurias-encephalopathy• CBS deficiency- thrombosis, connectivetissue disturbancessubstrátproduktDisorders of small andcomplex molecules

Small molecules in biochemicalgenetics• definition: < 1500 Da• gases, inorganic ions• amino acids• organic acids• saccharides• polyols• simple lipids• purines, pyrimidinesidi• vitamins• oligomers: peptides up to 5-10 AA, oligosaccharides• cytosol, mitochondrial stroma• blood, urineDiseases of small molecules• usually dependent on exogenous supply• manifestation: (repeated) acute toxicity, usuallywith encephalopathy/coma• hepatopathy common• common disturbances in routine labs-ammonia,Astrup, ketone bodies, glycemia, uric acid...• symptoms develop due to specific type of food,fasting, catabolism• chronic course possible (if toxicity low)• usually good therapeutic response to diet and/orvitaminsi

Isovaleric aciduria• FTT, vomiting, Kussmaulbreathing• consciousness: comawithin 24-48 h after onsetof symptoms• metabolic acidosis,ketonuria• sweaty feet syndromehttp://images.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/8/8b/Isovaleric_acid_structure.pngCystinuriahttp://www.nature.com/ki/journal/v73/n8/images/5002790f1.jpghttp://graphics8.nytimes.com/images/2007/08/01/health/adam/17046.jpg

Complex molecules in biochemicalgenetics• definition: > 1500 Da• glykolipids• sphingolipids• plasmalogens• neutral polysaccharides (glycogen)• mucopolysaccharides• (other polymers: proteins, nucleic acids...)• usually associated with membranes• concentrations in blood/urine rather low,exceptions exist ( x MS/MS technologie)Diseases of complex molecules• disease progresses usually regardless of anyexogenous sources from food• typical course is progressive (± symptom-freeperiod)• dysmorphy at birth possible• frequent involvement of nervous system andmusculature• organomegaly due to storage in lysosomalstorage disorders• usually untreatable by diet or vitamins

Mukopolysaccharidosis type Ihttp://eyepathologist.com/images/KL1771.jpghttp://deti.msk.ru/plaxin_egor.jpghttp://myweb.lsbu.ac.uk/dirt/museum/margaret/438-1811-2640151.jpg< 1500 Da > 1500 DaAcute toxicity Y NChronic progression ± YLocalization cytosol, ECT membranesImpact on structure N YDx blood,urine tissues (U)Origin exogenous endogenousRx-diet, vitamins efficious inefficious

Patophysiology IEMsubstrate1500 Daproduct1 23Clinical manifestation ofIEMs

Clinical picture-agehttp://www.hrr.co.uk/acatalog/crocodile_toddler.jpghttp://www.co.shasta.ca.us/html/DSS/images/FosterParentingAdopt/infant.jpghttp://markandrich.googlepages.com/Old-woman.jpg/Old-woman-full.jpgClinical features-organshttp://universe-review.ca/I10-82-organs.jpg

Selected common situations withhigh risk of IEM• Small molecules acutelly ill newborn (repeated) atack of long-term uncosciousness failure to thrive• Complex molecules progressive CNS and musculature involvement facial dysmorphy organomegaly (liver, spleen, heart)Food and IEMs (small molecules)• (sub)acute toxicitymilk (lactose)-hepatopathysaccharose/fructose/sorbitol- hepatopathyand hypoglycemiaexcess protein- vomiting, lethargy, coma(urea cycle disorders, organic acidurias)

Fasting and IEMs• hypoglycemia in GSD• hypoglycemia with decreased production ofketone bodies (beta-oxidation defects)• acidosis, ketonuria and metabolicencephalopathy p in prolonged fasting (organicacidurias)• respiratory alkalosis and encephalopathy (ureacycle disorders)Abnormal urinary smell and color• smell (small volatile molecules):• color• sweaty feet-isovalerate• maple syrup-branched ketoacids• boiled cabbage-methionine oxid• fish-trimethylamine• blackcurrant- organic acids• mouse-phenylacetate• orange-urate• black upon oxidation-homogentisate• blue-indoxyl derivaties• green-4-OH-butyrate

Common labs in IEMsBlood• glycemia• cholesterol• TG• uric acid• MAc• hyperammonemia, RAlk• ALT,AST• CK• anemia/pancytopeniaUrine• ketone bodies• uric acid• crystaluria• myoglobinuria1857-1936http://www.historiadelamedicina.org/imagenes/garrod.jpg