Information

PGD (PRE-IMPLANTATION GENETIC DIAGNOSIS)

Introduction

Each human cell, whether a blood cell, a skin cell, or a single cell from an embryo, contains all of our DNA, or genetic information. If you were to open a cell and take this information out you would notice that the genetic alphabet consists of only four letters, A, T, G, and C. It is the order in which these letters are put together that tells a cell what to be or do.

If you were to type out all the A, T, G and C’s in a cell, the whole genetic code, the finished document would be the equivalent of a 300 volume set of the Encyclopaedia Britanica – there is that much DNA in every one of our cells. Chromosomes are like the books of this genetic encyclopaedia. We have two copies of each, one from our mum and one from our dad, numbered 1 to 22, and either two X’s if we are female or an X and a Y if we are male, making a total of 23 pairs in each cell. Genes are like the paragraphs within these books, each with a defined beginning and end, and saying something unique. A genetic mutation is like a typing error, and most are no more than the change of a single letter in a single word of a single sentence of one of these thousands of paragraphs. Consider changing the first letter of the word GOAT to COAT – that single letter change means something very different. Such small changes can have major consequences when coding for an important function in a cell.


What is PGD?

Pre-implantation Genetic Diagnosis (PGD) is a technology which allows genetic testing of an embryo prior to implantation and before pregnancy occurs.
Some couples are at risk of transmitting an inherited disease to their children. One of the couple may be affected by this disease, or they each may carry a mutation, which if both were inherited by a child would cause the disease. Developed in the early 1990’s Pre-implantation genetic diagnosis (PGD) is a way of detecting a specific disease-causing genetic mutation within an embryo before it is transferred to the womb and forms a pregnancy.

PGD can also be used to tissue match an embryo if a couple already have a child affected by a genetic disease that can be cured using stem cells from an HLA identical sibling. HLA is a genetic fingerprint on white blood cells and platelets, composed of proteins that play a critical role in activating the body’s immune system to respond to foreign organisms.
Couples undergo routine IVF and ICSI, and when their embryos are three days old usually one cell is removed for genetic testing. These cells are sent to the genetics lab, where the DNA, genetic information, from the cells is read to see if the embryo will be affected by the disease and if they are a HLA match. Healthy, unaffected embryos can be replaced in the womb when they are five or six days old.

What can PGD test for?

In the UK, fertility treatment and PGD are regulated by the Human Fertilisation and Embryology Authority (HFEA). Centres require a license to perform PGD. PGD can be been used for over 200 genetic conditions, some of which are listed below.
Achondroplasia (FGFR3)
Adrenoleukodystrophy (ABCD1)
Agammaglobulinemia-Bruton (TyrsKnse)
Alpha Thalassemia (HBA1)
Alpha-Antitrypsin (AAT)
Alport Syndrome (COL4A5)
Alzheimer (very early onset-PSEN1)
Beta Thalassemia (HBB)
Bloom Syndrome (Blm)
Canavan Disease (ASPA)
Charcot Marie Tooth Neuropathy - 2E
Charcot-Marie-Tooth Neuropathy - 1B
Choroideremia (CHM)
Chronic Granulomatous Dz (CYBB)
Citrullinemia (ASS)
Cleidocranial Dysplasia (RUNX2)
Congen. Adrenal Hyperplasia (CYP31A2)
Congen. Erythropoietic Porphyria (UROS)
Crigler Najjar (UGT1A1)
Cystic Fibrosis (CFTR)
Darier Disease (ATP2A2)
Diamond Blackfan (DBA-RSP19)
Diamond Blackfan (DBA2)
Duchenne muscular dystrophy (DMD)
Dystrophy Myotonica (DMPK)
Emery-Dreifuss Muscular Dystrophy
Epidermolytic Hyperkeratosis (KRT10)
Factor 13 Deficiency (F13A1)
Familial Adenomatous Polyposis (APC)
Familial Dysautonomia (IKBKAP)
Fanconi Anemia A (FANCA)
Fanconi Anemia C (FANCC)
Fanconi Anemia F (FANC F)
Fanconia Anemia G (FANCG)
Fragile X (FMR1)
Friedreich Ataxia I (FRDA)
Gaucher Disease (GBA)
Glutaric Acidemia - 2A
Hemophilia A (F8)
Hemophilia B (F9)
HLA DRBeta1 Class II MHC (HLA DRB1*)
HLA-A Class I MHC (HGNC HLA-A )
Hunter syndrome (IDS)
Huntington Disease (HD)
Hurler Syndrome (MPSI-IDUA)
Hyper IgM (CD40-ligand; TNFSF5)
Hypophosphatasia (ALPL)
Incontinentia Pigmenti (KBKG-NEMO)
Kennedy Disease (AR)
Krabbe (GALC)
Lesch-Nyhan (HPRT1)
Leukemia (for HLA)
Leukocyte Adhesion Deficiency (ITGB2)
Li-Fraumeni Syndrome (TP53)
Lymphoproliferative Disorder (X-linked)
Marfan Syndrome (FBN1)
Menkes (ATP7A)
Metachromatic Leukodystrophy (ARSA)
Mucolipidosis 2 (I-Cell)
Neurofibromatosis (NF1 & NF2)
Niemann-Pick type C (NPC1)
Ornithine Transcarbamylase Deficiency (OTC)
Osteogenis Imperfecta (COL1A1)
Pachyonychia Congenita (KRT16 & KRT6A)
Periventricular Heteropia (PH)
Polycystic Kidney Disease (AR-PKD1)
Polycystic Kidney Disease (PKD1)
Retinoblastoma 1 (RB1)
Rhesus blood group D (RHD)
Rhizomelic Chondrodysplasia Puncta RCDP1
Sacral Agenesis (HLXB9)
Sanfilippo A (MPSIIIA)
SCID-X1 (SevereCmbndImmuneDefic)
(IL2RG)
Sexing for X-linked Dz (AMELX/Y; ZFX/Y)
Shwachman-Diamond Syndrome (SBDS)
Sickle Cell (HBB)
Smith-Lemli-Opitz (SLOS)
Spinal muscular atrophy (SMN1)
Spinocerebellar
Ataxia-3 (SCA3)
Spinocerebellar ataxia2 (SCA2)
Tay-Sachs (HEXA)
Treacher Collins (TOCF1)
Tuberous Sclerosis 1 (TSC1)
Wiskott-Aldrich Syndrome (WAS)
10591 V 1.0