Aberrant tyrosine transport across the fibroblast membrane in patients with schizophrenia –indications of maternal inheritance

BackgroundIn previous studies of the present patients with schizophrenia, aberrant tyrosine transport across the fibroblast membrane was found. A low Km, a kinetic factor indicating high affinity between tyrosine and the binding site at the cell membrane, was found to be associated with poor cognitive functions in patients. The present study aimed at investigating possible relationships between patients with schizophrenia and their first-degree relatives in aberrant tyrosine transport indicating that it may be a biological marker for the genetic susceptibility.MethodsThirty-three parents, 13 fathers and 20 mothers, from 23 families with a schizophrenic patient agreed to enter the study. They underwent skin biopsies for fibroblast cultivation, neuropsychological and psychiatric investigations and were classified as family history positive or negative. Tyrosine transport kinetics (Km and Vmax) were calculated from in vitro trials of gradients of extracellular tyrosine concentrations in fibroblast cultures.ResultsAn association between patients with schizophrenia and their mothers were found for a low Km indicating maternal inheritance. Mothers displaying a low Km performed worse on the neuropsychological tests compared to mothers with normal Km. Corresponding relationships between a low Km and neurocognitive dysfunction had previously been found for the patients.ConclusionsAn aberrant tyrosine transport across plasma membrane may constitute a biological marker for an endophenotype within the schizophrenia spectrum with low cognitive functioning. A plausible mode for genetic transmission is maternal inheritance.