Kell and XK immunohistochemistry in McLeod myopathy

Abstract

The McLeod syndrome is an X-linked neuroacanthocytosis manifesting with myopathy and progressive chorea. It is caused by mutations of the XK gene encoding the XK protein, a putative membrane transport protein of yet unknown function. In erythroid tissues, XK forms a functional complex with the Kell glycoprotein. Here, we present an immunohistochemical study in skeletal muscle of normal controls and a McLeod patient with a XK gene point mutation (C977T) using affinity-purified antibodies against XK and Kell proteins. Histological examination of the affected muscle revealed the typical pattern of McLeod myopathy including type 2 fiber atrophy. In control muscles, Kell immunohistochemistry stained sarcoplasmic membranes. XK immunohistochemistry resulted in a type 2 fiber-specific intracellular staining that was most probably confined to the sarcoplasmic reticulum. In contrast, there was only a weak background signal without a specific staining pattern for XK and Kell in the McLeod muscle. Our results demonstrate that the lack of physiological XK expression correlates to the type 2 fiber atrophy in McLeod myopathy, and suggest that the XK protein represents a crucial factor for the maintenance of normal muscle structure and function.

Neuroacanthocytosis: new developments in a neglected group of dementing disorders

“…In an immunohistochemical study, McLeod skeletal muscle failed to show a specific staining pattern for XK and Kell, in contrast to controls where Kell immunohistochemistry stains sarcoplasmic membranes and XK immunohistochemistry shows a type 2 fiber-specific intracellular staining. XK protein may play a crucial role for the integrity of normal muscle [75].…”

Cerebral Metabolic Alterations in McLeod Syndrome

“…Neurological examinations revealed consistently absent tendon reflexes reflecting subclinical sensorimotor axonopathy. Only 1 patient (IV-13) had a manifest myopathy, and none had cardiac manifestations (table 1) [6]. Three male McLeod patients (IV-4, IV-5, IV-13) had predominant psychiatric or cognitive manifestations.…”

“…Neuromuscular manifestations may be subclinical or mild, and include myopathy, cardiomyopathy and sensorimotor axonal neuropathy [4,5,6]. Central nervous system manifestations resemble Huntington’s disease and comprise a choreatic movement disorder, psychiatric symptoms, subcortical cognitive decline, and generalized epileptic seizures [1, 3, 4].…”

Cardiac abnormalities in McLeod syndrome

“…The XK gene shares important homologies with the ced-8 gene of the nematode C. elegans where it is a cell death effector downstream of the caspase ced-3 [8]. Therefore, apoptosis dysregulation might represent a cause for the neurodegeneration in the McLeod syndrome [9]. Based on the findings of compensated hemolysis and erythrocyte acanthocytosis in McLeod patients, loss of cell membrane integrity and cytoskeletal changes have to be discussed as alternative pathogenetic pathways contributing to a novel cardiomyopathic mechanism.…”