Nuclear Protein Assay Kit
Mammalian sperm and DNA is the most compacted eukaryotic DNA, which is in sharp contrast to DNA structure in somatic cells nuclei.
Compaction and organization help protect sperm chromatin during transport through the male and female reproductive tract. This also ensures delivery of the paternal genome in a form that allows developing embryo to accurately express genetic information.
Somatic cell nuclear DNA is wrapped around an octamer of histones and packaged into a solenoid structure. This type of packaging adds histones which increase the chromatic volume.
During spermiogenesis, sperm chromatic undergoes a series of modifications in which histones are lost and replaced by protamines.
Protamines are approximately half the size of histones. They are highly basic spermspecific nuclear proteins that are characterized by an argininerich core and cysteine residues.
Protamines condense the DNA strands and form the basic packing unit of sperm chromatin called a toroid. Thereby, conferring a higher order of DNA packaging in sperm than that found in somatic cells.
Humans express equal quantities of two protamines, protamine 1 and protamine 2. The mean P1 / P2 ratio is approximately 1.
In human chromatic, ~85% of the histones are replaced by protamines. Approximately 15% of the histones are retained subsequently making chromatin less tightly compacted.
During spermatogenesis, first somatic histones are replaced by testisspecific histone variants, which are replaced by transition proteins (Tp1a and TP2) in a process involving extensive DNA rearrangement and remodeling. During the elongating spermatid stage, the transition proteins are replaced in the condensing chromatin by protamines.
Chromatin remodeling is facilitated by the coordinated loosening of the chromatin by histone hyperacetylation and by the DNA topoisomerase II (tope II), which product temporary nicks in the sperm DNA to relieve torsional stress that results from super coiling. The same enzyme Topo II normally repairs these temporary nicks prior to completion of spermiogenesis and ejaculation. However, if these nicks are not repaired, DNA fragmented sperm may be present in the ejaculate.
Defects in the chromatin remodeling process result in the production of spermatozoa that are characterized by reduction in the efficiency of protamination, abnormal protamine 1 to protamine 2 ration, and relatively high nucleohistone content. Thereby, creating a state of vulnerability where spermatozoa DNA become increasingly susceptibly to oxidative damage.
Abnormal Protamine P1 / P2 ratio is associated with low sperm count, decreased sperm motility and morphology, diminished fertilization ability, and increased sperm chromatin damage.
Sperm nuclear protein assay (chromatin maturity) is done via Aniline Blue staining. Aniline Blue stains persistent histones in the sperm nucleus.
- Mature Chromatin. Histone <15% and Protamine (I and II) >85%