In Australian Shepherd Dogs
What is Pelger-Huet Anomaly?
It should not be confused with pseudo-Pelger-Huet Anomaly, which can result from myeloid leukemia, myelodysplasia, and bi-lineage acute lymphocytic leukemia, after considerable chemotherapy treatments, as well as certain deficiencies or excesses of substances. It is not a heritable disease, but appears very similar to the true Pelger-Huet Anomaly.
What Causes Pelger-Huet Anomaly?
It is similar to the double merle gene in Australian Shepherds in its lethal form, and is thought to have developed because genes have been inadvertently concentrated due to selective breeding.
The gene responsible for the Pelger-Huet anomaly is the LBR (Lamin B receptors) gene on subband 1q42.1, first discovered in crossbreeding experiments with rabbits in Germany. The gene product of LBR is responsible for maintaining nuclear membrane structure. Homozygous dominant individuals have very coarsely and tightly bound neutrophils that are typically not capable of normal function. Heterozygous individuals have neutrophils with lobed, dumbell shaped nuclei, also called "pince-nez" because of their similarity to pinched nose spectacles.
LBR interacts with the heterochromatin proteins, which is thought to be the cause for the excessive clumping of chromatin observed. These abnormalities in heterozygous individuals do not seem to effect neutrophil function and the cells can phagocytize normally. Homozygous individuals are very rare, but when they do occur, have neutrophils that are a single round shape with eccentric nuclei, clumped chromatin, and and little to no segmentation.
Homozygous vs. Heterozygous Individuals
In the very rare case that a homozygous individual does survive past puppyhood, it is susceptible to skeletal anomalies, developmental delays, and seizures.
Is it ethical or worthwhile to breed to another heterozygous female carrier who was equally prestigious in her awards and accomplishments, if her owner approached you and asked if you would allow a breeding to your sire?
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