DEVELOPMENTAL GENETICS, BIRTH DEFECT & PRENATAL DIAGNOSIS M. Mansyur Romi Departemen Anatomi, FK UGM Tim Genetika Klinik RSUP DR.SARDJITO YOGYAKARTA

The Genetic Basis of Development How do cells with the same genes grow up to be so different?

Three Procceses of Development The transformation from a zygote into an organism Results from three interrelated processes: cell division, cell differentiation morphogenesis Figure 21.3a, b (a) Fertilized eggs of a frog (b) Tadpole hatching from egg

Through a succession of mitotic cell divisions The zygote gives rise to a large number of cells In cell differentiation Cells become specialized in structure and function Morphogenesis encompasses the processes That give shape to the organism and its various parts

Differential gene expression Nearly all the cells of an organism have genomic equivalence, that is, they have the same genes Differences between cells in a multicellular organism differences in gene expression not from differences in the cells’ genomes

Cell Differentiation yields a variety of cell types Cell Differentiation yields a variety of cell types each expressing a different combination of genes multicellular eukaryotes cells become specialized as a zygote develops into a mature organism

Cell Diferentiation Different types of cells Cell Diferentiation Different types of cells Make different proteins because different combinations of genes are active in each type Muscle cell Pancreas cells Blood cells

Differentiated cells may retain all of their genetic potential Differentiated cells may retain all of their genetic potential Most retain a complete set of genes May be totipotent

The Stem Cells of Animals A stem cell Is a relatively unspecialized cell Can reproduce itself indefinitely Can differentiate into specialized cells of one or more types, given appropriate conditions

Embryonic and Adult Stem Cells Early human embryo at blastocyst stage (mammalian equiva- lent of blastula) From bone marrow in this example Pluripotent cells Cultured stem cells Different culture conditions types of differentiated Blood cells Embryonic stem cells Adult stem cells Stem cells can be isolated From early embryos at the blastocyst stage Adult stem cells pluripotent, able to give rise to multiple but not all cell types Totipotent cells Liver cells Nerve cells

Transcriptional Regulation of Gene Expression During Development Transcriptional Regulation of Gene Expression During Development Complex assemblies of proteins control eukaryotic transcription A variety of regulatory proteins interact with DNA and with each other To turn the transcription of eukaryotic genes on or off

Transcription Factors Transcription Factors Assist in initiating eukaryotic transcription Enhancers Promoter Gene DNA Activator proteins Transcription factors Other proteins RNA polymerase Bending of DNA Transcription

Cytoplasmic Determinants and Cell-Cell Signals in Cell Differentiation Cytoplasmic determinants in the cytoplasm of the unfertilized egg Regulate the expression of genes in the zygote that affect the developmental fate of embryonic cells Molecules of another cyto- plasmic deter- minant Sperm Unfertilized egg cell Sperm Molecules of a a cytoplasmic determinant Cytoplasmic determinants in the egg. The unfertilized egg cell has molecules in its cytoplasm, encoded by the mother’s genes, that influence development. Many of these cytoplasmic determinants, like the two shown here, are unevenly distributed in the egg. After fertilization and mitotic division, the cell nuclei of the embryo are exposed to different sets of cytoplasmic determinants and, as a result, express different genes. Fertilization Nucleus Zygote (fertilized egg) Mitotic cell division Two-celled embryo

Induction Signal molecules from embryonic cells cause transcriptional changes in nearby target cells Induction by nearby cells. The cells at the bottom of the early embryo depicted here are releasing chemicals that signal nearby cells to change their gene expression. (b) Early embryo (32 cells) NUCLEUS Signal transduction pathway Signal receptor Signal molecule (inducer)

Pattern Formation Pattern formation in animals and plants results from similar genetic and cellular mechanisms Pattern formation Is the development of a spatial organization of tissues and organs Occurs continually in plants Is mostly limited to embryos and juveniles in animals

Cell Positioning Positional information Consists of molecular cues that control pattern formation Tells a cell its location relative to the body’s axes and to other cells

THE GENETIC CONTROL OF EMBRYONIC DEVELOPMENT Cascades of gene expression and cell-to-cell signaling direct the development of an animal Early understanding of the relationship between gene expression and embryonic development Came from studies of mutants of the fruit fly Drosophila melanogaster Eye Antenna Leg SEM 50 Head of a normal fruit fly Head of a developmental mutant

What Are Birth Defects? Birth defects are defined as abnormalities of structure, function, or body metabolism that are present at birth. These abnormalities lead to mental or physical disabilities or are fatal. There are more than 4,000 different known birth defects ranging from minor to serious, and although many of them can be treated or cured, they are the leading cause of death in the first year of life.

What Are Birth Defects? Birth defects are defined as abnormalities of structure, function, or body metabolism that are present at birth. These abnormalities lead to mental or physical disabilities or are fatal. There are more than 4,000 different known birth defects ranging from minor to serious, and although many of them can be treated or cured, they are the leading cause of death in the first year of life.

Birth Defects 3% of all live-born infants have an major anomaly Some babies survive the pregnancy but are born with serious problems called birth defects. 3% of all live-born infants have an major anomaly Additional anomalies are detected during postnatal live – about 6% at 2 year-olds, 8% in 5year-olds, other 2% later Single minor anomalies are present in about 14% of newborns

Birth defects Major anomalies are more common in early embryos (up to 15%) than they are in newborns (3%). Most severely malformed embryos are spontaneously aborted during first 6 to 8 weeks. Some birth defects include: Cerebral Palsy Cleft Lift and/or palate Down Syndrome Muscular Dystrophy Sickle Cell Anemia Spina Bifida and more!

Causes of Birth Defects Some causes are environmental because it is during the first few weeks that a baby develops all the bodily systems needed for survival The mother’s diet Any diseases or infections the mother has Harmful substances Some medicines Exposure to hazards (such as chemicals, X-rays, etc.) Some causes are hereditary Sometimes a child inherits a defective gene that is dominant such as Huntington's Some conditions affect only one sex and usually it’s the males Hemophilia Color blindness and more

More Causes of Birth defects Errors in chromosomes Such as when a baby has too many or too few chromosomes or has broken or rearranged chromosomes This usually leads to Down Syndrome

Problems in Prenatal Development Sometimes a pregnancy begins, but a baby doesn’t develop normally If the baby dies before the 20th week it is called a miscarriage If the baby dies after that time, it is called a stillbirth. 15-20% of recognized pregnancies end in miscarriage 2% ends in stillbirth

Pertanyaan klasik: Peralatan lama: ? Kelamin janin ? ? Janin normal ? Variabel ukuran uterus Kenaikan BB ibu Auskultasi jantung janin

Peralatan abad XX 1950an: analisis sel janin dr cairan amnion utk keberadaan sex chromatin 1966: kultur sel dr cairan amnion 1972: USG utk diagnosis anencephaly Saat ini USG mampu menilai hampir seluruh anatomi janin

Penafsiran diagnosis pranatal bergantung: Sampel yg dapat diperoleh Teknik yg dapat dipakai Informasi yg dapat diolah

Ragam sampel: Serum maternal, untuk: Cairan amnion, untuk: Penanda (marker) cerminan kesehatan janin Protein yg berasal dr janin Cairan amnion, untuk: Bahan yg dpt dianalisis (analytes) Sel yg berasal dr janin Villus chorion, untuk: sel trofoblast Sel darah janin: eritrosit & lekosit

Teknik yg dipakai Sampling darah maternal Amniocentesis Chorionic villous sampling (CVS) Cordocentesis Ultrasonography (USG) Embryo biopsy

Penapisan (screening) serum maternal Alfa fetoprotein (AFP) Produksi dlm hepar janin, puncak: mgg 10-13 Dlm darah maternal lewat placenta atau difusi menembus membran Konsentrasi puncak : mgg 24-32

Some causes of increased maternal serum AFP concentration Undersestimated gestational age Threatened abortion Multiple pregnancy Fetal abnormality: anencephaly, open neural tube defect, anterior abdominal wall defect, Turner’s syndrome, bowel atresias, skin defects Placental hemangioma Decreased matenal serum AFP concentration: Trisomy 21, 18

Triple screen: AFP Human chorionic gonadotropin (HCG) Disekresi embryo baru implantasi Unconjugated estrogen (UE)

Amniocentesis Cairan amnion volume> dg usia: 15-350 ml berisi: urin janin + bahan maternal normal steril dan tahan infeksi perlakuan umumnya pd trimester dua dg risiko kematian janin 0,5 % perlakuan dini: mgg 12-15 dg risiko 2-11%

amniocentesis

Indikasi Analisis kromosom dari sel amnion yang dikultur: trisomi 21 dsb Estimasi konsentrasi AFP dan aktifitas acetylcholin esterase (Ache): neural tube defects Analisis biokimiawi cairan amnion dan sel kultur: inborn error of metabolism

CVS Sel trofoblas: cermin status genetik janin cepat berproliferasi, tak perlu kultur sumber utk: karyotype pemeriksaan DNA pengukuran aktifitas enzim yg diekspresi derivat fibroblast perlakuan mgg 9-11 dg risiko kematian janin 2-13%

Chorionic Villus Sampling (CVS)

Indication for CVS Diagnosis of chromosomal disorders Increasing number of inborn error of metabolism DNA analysis

Cordocentesis Dilakukan bila cara lain utk mdpt sel janin takcukup atau serum fetal sangat perlu dikaji sel janin utk: karyotyping bila dg cara lain tampak mosaicism darah janin utk: mengukur protein serum hanya di pusat sangat khusus, risiko kematian janin 0-3%

USG Informasi anatomis dan fungsional janin mengungkap struktur: kepala, thorax, abdomen, skeleton dan pertumbuhan janin real time usg: struktur & aktifitas jantung modern usg utk rincian anatomi janin: ukuran & posisi ruang jantung, ventriculus cerebri, aorta & a.pulmonalis

MENGAPA PERLU MEMPELAJARI GENETIKA? Pergeseran pola : penyakit ‘lingkungan ‘(malnutrisi & infeksi) menurun, penyakit degeneratif & genetik meningkat Terungkapnya peran faktor genetik sebagai penyebab penyakit pada manusia Turunnya angka kematian bayi: Indonesia: 142%o(71)67%o(91), DIY:62%o(‘80)26%o(‘92)15,5%o(‘00) Meluasnya konsep keluarga kecil

Genetically determined diseases Chromosomal disorders Single gene disorders Polygenic or multifactorial diseases Somatic cell genetic disorders Mitochondrial genetic disorders

RAGAM PENYAKIT GENETIK KELAINAN KROMOSOMAL Pada umumnya jarang Pola pewarisan tidak jelas Biasanya resiko kerabat rendah KELAINAN GEN TUNGGAL/MONOGENIK Jumlah ragamnya banyak, masing-masing kasusnya sedikit Pola pewarisan jelas, ikuti hukum Mendel Resiko kerabat tinggi

PENYAKIT POLIGENIK/MULTIFAKTORIAL Banyak dijumpai Pola pewarisan tidak jelas Resiko kerabat rendah-sedang KELAINAN MUTASI SEL SOMATIK Mungkin ada gambaran “mosaik” Menyebabkan neoplasia/keganasan KELAINAN GEN MITOKHONDRIA Pola pewarisan”maternal”atau sporadic

Birth defects Major anomalies are more common in early embryos (up to 15%) than they are in newborns (3%). Most severely malformed embryos are spontaneously aborted during first 6 to 8 weeks. Some birth defects include: Cerebral Palsy Cleft Lift and/or palate Down Syndrome Muscular Dystrophy Sickle Cell Anemia Spina Bifida and more!