Haplotypes of Holstein Cattle HH1-HH7

Haplotype mutations are lethal recessive defects found in the Holstein-Friesian cattle breed. They manifest themselves in homozygous individuals with two copies of mutant alleles. They contribute to abnormal embryonic development and abortion of unborn individuals. They can be passed on to offspring without major signs, which has led to a cycle of reaction to eliminate these genetic defects in the Holstein cattle population.

The HH1 haplotype located within chromosome 5 (BTA 5) is responsible for the mutation of the APAF1 protein, contributing to the shortening of its structure. Such a condition leads to serious consequences of developmental and neurodegenerative disorders of the embryo in cattle, leading to its death before birth.

The HH2 haplotype located on chromosome 1 (BTA 1) determines the development of a mutation in the gene encoding the IFT80 protein. This mutation results in the truncation of the protein by an extensive number of amino acids, consequently leading to an imbalance in transport across cell membranes, for which the IFT80 protein is responsible along with the rest of the IFT group subunits. The disorders affect the process of embryonic development contributing to the inability of the body’s cells to function properly and embryonic death.

The HH3 haplotype maps to chromosome 8 (BTA 8). It determines the occurrence of a mutation within the SMC2 gene, caused by an amino acid substitution in the sequence. The encoded SMC2 protein is responsible for a key role in DNA regulation and repair, closely linked to chromosome condensation during cell division. Lack of a properly formed protein leads to loss of embryonic viability.

The HH4 haplotype located on chromosome 1 (BTA 1), responsible for the mutation of the GART protein, caused by an amino acid swap in the sequence. The encoded protein is involved in the synthesis of purines, which are essential components of DNA, RNA and ATP molecules. The mutation leads to a loss of function of the GART protein, thereby leading to the death of the embryo after fertilization.

The HH5 haplotype is located on chromosome 9 (BTA 9). The mutation is caused by a deletion in the region encoding the TFB1M transferase protein. TFB1M is crucial for protein translation in mitochondria. Lack of a fully functional transferase leads to destabilization of ribosomes and disruption of protein biosynthesis, leading to fatal consequences for the embryo.

The HH6 haplotype mapped on chromosome 16 (BTA 16) is responsible for a mutation in the gene encoding the SDE2 protein, essential for maintaining telomere stability in eukaryotic organisms. The mutation leads to dysfunction of the SDE2 protein by shortening its structure, which contributes to impaired embryonic growth and death.

The HH7 haplotype located on chromosome 27 (BTA27) determines the mutation responsible for the nucleotide deletion in the CENPU protein structure. The encoded centromere protein U is a component of the centromere, essential for proper chromosome segregation during mitosis. The mutation causes defects in mitotic division and leads to early embryonic death.

REFERENCES #

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