Glossary of Scientific Terms

4q35. A cytogenetic term that defines the “address” of the chromosomal deletion associated with FSHD Type 1. The deletion is on chromosome 4, on the “q” (long) arm at region 35.

4q35 genes. A group of genes located in the 4q35 region, some whose activity is regulated by the D4Z4 repeat array.

Allele. An alternative genetic sequence at a given chromosome location, governing the same physical trait. Typically you inherit one allele form your mother and one allele from your father.

Antibody. Proteins produced by the immune system, which bind specifically to unique features of other proteins and macromolecules.  Exploited by the immune system to destroy foreign materials, and by scientists to identify specific molecules.

Antisense oligomers. Single stranded chains of nucleotides that bind to a specific sequence of RNA, thereby preventing its genetic information from being expressed.

Autophagy. The degradation of unnecessary or dysfunctional cellular components via the lysosome (compartments inside the cell that digest cellular waste).

Binding. The interaction of one molecule to another, which causes a change in the shape and function of the target molecule.

Biomarker. Objective measurements that indicate a patient’s health status, such as tests of muscle strength, a blood test, imaging, etc. Diagnostic biomarkers show if a person has a disease. Therapeutic biomarkers show if a therapy is having the desired effect.

Chromatin. The combination of DNA and proteins (primarily histones) that make up the contents of the nucleus of a cell. The main functions of chromatin are to package DNA into a smaller volume, to strengthen the DNA to allow cell division, to prevent DNA damage, and to control gene expression and DNA replication.

Chromosome. Found inside the cell nucleus, a recognizable structure comprising chromatin-containing genes, regulatory elements and other nucleotide sequences. In humans, each cell nucleus contains 23 distinct pairs of chromosomes.

Clinical trial. Tests of drugs, diagnostics and other health interventions in human volunteers conducted to generate safety and efficacy data.

Cytoplasm. The cytoplasm is the jelly-like part of the cell lying between the cell membrane and the nuclear membrane.

D4Z4. A repeated DNA segment of approximately 3,200 nucleotide bases. The number of repeats can vary significantly in different individuals and can be used to predict FSHD status. Loss of these repeats at chromosome locus 4q35 is associated with FSHD Type 1. Each D4Z4 contains a DUX4 gene. (D4Z4 gets its name from: D for DNA segment (of unknown or ‘anonymous’ nature); 4 for chromosome 4; Z to distinguish it from S (which represents a single sequence occurrence) and represents a repetitive-type sequence entity; 4 representing the fourth member of this ‘class’ of sequences identified on chromosome 4.)

Deletion. Loss of part of a DNA molecule, as in “deletion of D4Z4 repeats at 4q35” associated with FSHD.

Differentiation. The process by which a less specialized cell (e.g. in an embryo) becomes a more specialized cell type, such as skin, heart, muscle, or neuron. In adults, stem cells divide and differentiate into daughter cells during wound healing and normal cell turnover.

DNA. The molecule that defines our genetic inheritance. It contains all the instructions for constructing and operating a living organism. DNA is made of four simple units, or “nucleotide bases”, whose specific sequence “spells out” genetic information.

DUX4 (Double homeobox, 4). A copy of the DUX4 gene is located within each D4Z4 repeat array on chromosome 4. Inappropriate expression of DUX4 in muscle cells is thought to be a contributor to FSHD.

Epigenetics. Refers to chromatin modifications that change gene function without changing the underlying DNA sequence. Examples of these modifications are DNA methylation and histone modification, both of which serve to regulate how a gene becomes expressed as protein. Some of these changes have been shown to be heritable.

Expression profiling. The first step in converting genetic information to an observable trait involves the transfer of information from gene to protein through an intermediate molecule called RNA. Measuring all of the RNA produced in one definable moment, to create a global picture of cellular function produces a profile of total expression activity.

FISH (fluorescent in situ hybridization). A laboratory technique, commonly employed in the field of cytogenetics, that uses fluorescent probes to detect and localize the presence of specific DNA sequences on chromosomes.

Gene. The basic unit of heredity defined by specific segment of DNA. Genes specify the instructions needed to produce an observable trait.

Gene expression. The initial step in converting the information contained in a gene, as DNA, to an observable character through an intermediate molecule RNA.

Gene locus. Physical location of a gene on a chromosome.

Genotype. The actual DNA sequence a cell, an organism, or an individual, usually with reference to a specific characteristic under consideration.

Germ line. The collection of biological cells that give rise to gametes (egg or sperm).

Homeobox.  A DNA sequence found within genes that are involved in the regulation of patterns of anatomical development in organisms.

Histones. The chief protein components of chromatin, acting as spools around which DNA winds. Play a role in gene expression.

Immortalized cells. Cells that continue to divide indefinitely, unlike normal cells which with normal aging cease to divide.

Immunocompromised. A state in which the immune system is defective and unable to mount an immune response against disease pathogens or other foreign cells.

Innervate. Formation of a functional connection between nerve and muscle or other target tissue.

Longitudinal study. A research study involving repeated observations of the same variables in the same individuals over long periods of time.

Lysosome. Cellular organelle that contain enzymes that break down waste materials and cellular debris.

Magnetic resonance imaging (MRI).medical imaging technique using the property of nuclear magnetic resonance to image nuclei of atoms inside the body. MRI can create more detailed images of the human body than are possible with X-rays.

Magnetic resonance spectroscopy (MRS). A research technique using nuclear magnetic resonance to provide information about chemical properties of atoms and molecules.

Methylation. In biological systems, the addition of a methyl group to DNA, which can regulate the expression of genes. Some methylation changes are heritable.

Molecular pathway. A chain of chemical reactions occurring within a cell.

Mutation.  A change in the nucleotide sequence in the genome of an organism with perceived deleterious effects.

Myocyte. Long, tubular cells found in muscle. Myocytes develop from myoblasts to form skeletal muscle fibers (myotubes) in a process known as myogenesis.

Nucleus. A large cellular organelle enclose by a membrane that contains the genetic material (DNA).

Organelle. A specialized subunit within a cell that has a specific function.

Pathophysiology. Physiological processes or mechanisms whereby disease develops and progresses.

Phenotype. The composite of an organism’s observable characteristics or traits, such as its physical form, growth, biochemical and physiological properties, and behavior.

Pluripotent cells. A stem cell that has the potential to differentiate into diverse types of cells. Induced pluripotent stem cells (iPS cells or iPSCs) are a type of pluripotent stem cell artificially derived from an adult somatic cell, by inducing a “forced” expression of certain genes.

Polycomb. A family of proteins that can alter chromatin such that genes are epigenetically silenced (not able to be expressed).

Protein. Biological molecule consisting of linear chains of amino acids. Proteins are the principal products of genetic information and they do the bulk of work required for life. They perform a vast array of functions within living organisms, including providing cells with structure, mediating biochemical reactions, transmitting biological signals, and transporting molecules from one location to another.

Protein synthesis. The cellular production of proteins using information encoded in genes. The genetic code on DNA is transcribed into messenger RNA, and then translated into a chain of amino acids to form protein.

Reprogramming. Conversion of a cell from one cell type to another. This involves a conversion first to a pluripotent state, then re-differentiating to the new cell type.

RNA (Ribonucleic acid). A family of large biological molecules that perform vital roles in the codingdecodingregulation, and expression of genes. Like DNA, RNA is assembled as a linear chain of nucleotide “bases”, but is usually single-stranded.

Somatic cell. In multicellular organisms, any biological cell forming the body, other than a stem cell or germ line (reproductive) cell.

Stem cell.  Undifferentiated biological cells that can differentiate into a variety specialized somatic cells (pluripotent)  and can divide to produce more stem cells.

Target.protein or nucleic acid (DNA or RNA) whose activity can be modified by an external stimulus, such as a drug or another biological molecule (e.g. hormone, antibody, neurotransmitter, etc.).

Telomere. A region of repetitive nucleotide sequences at the tip of the arm of a chromosome, which protects the end of the chromosome.

Transcription. The copying of DNA into messenger RNA in gene expression.

Transgenic. An organism that has had exogenous genetic material (or transgene) introduced into its genome so that it will exhibit a new property.