Lipid contaminants: Polypropylene apparatus and vacuum pumps

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141137/1/lipd0192.pd

Lactosylceramide galactosidase: Comparison with other sphingolipid hydrolases in developing rat brain

Four enzyme assays were carried out with brains from rats of age 4 days to about 320 days. The enzymes were acid hydrolases: lactosylceramide galactosidases, galactosylphenol galactosidase, glucosylceramide glucosidase,a nd sphingomyelin phosphocholine hydrolase. The first two activities (based on wet brain weight) rose with age until about 24 days, then declined moderately; this curve parallel somewhat the curve for ganglioside concentration in brain. It is suggested that this parallelism supports the idea that lysosomal enzymes function in normal turnover. The other two enzymes studied showed a steadily declining activity with increasing age. It was found that the brain cytosol contained 12% or less of the galactosidase activiti, the value increasing somewhat in older rats. Most of the particulate galactosidase activities could be dispersed by sonication. The similarities between the two galactosidase activities suggest that most of the hydrolysis of the galactosylphenol is carried out by the lactosylceramide hydrolase. A procedure is given for preparing [3H]lactosylceramide labeled in the galactose portion of the molecule and for the assay of its hydrolase.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32942/1/0000325.pd

Heterozygous missense variants of LMX1A lead to nonsyndromic hearing impairment and vestibular dysfunction

Unraveling the causes and pathomechanisms of progressive disorders is essential for the development of therapeutic strategies. Here, we identified heterozygous pathogenic missense variants of LMX1A in two families of Dutch origin with progressive nonsyndromic hearing impairment (HI), using whole exome sequencing. One variant, c.721G > C (p.Val241Leu), occurred de novo and is predicted to affect the homeodomain of LMX1A, which is essential for DNA binding. The second variant, c.290G > C (p.Cys97Ser), predicted to affect a zinc-binding residue of the second LIM domain that is involved in protein–protein interactions. Bi-allelic deleterious variants of Lmx1a are associated with a complex phenotype in mice, including deafness and vestibular defects, due to arrest of inner ear development. Although Lmx1a mouse mutants demonstrate neurological, skeletal, pigmentation and reproductive system abnormalities, no syndromic features were present in the participating subjects of either family. LMX1A has previously been suggested as a candidate gene for intellectual disability, but our data do not support this, as affected subjects displayed normal cognition. Large variability was observed in the age of onset (a)symmetry, severity and progression rate of HI. About half of the affected individuals displayed vestibular dysfunction and experienced symptoms thereof. The late-onset progressive phenotype and the absence of cochleovestibular malformations on computed tomography scans indicate that heterozygous defects of LMX1A do not result in severe developmental abnormalities in humans. We propose that a single LMX1A wild-type copy is sufficient for normal development but insufficient for maintenance of cochleovestibular function. Alternatively, minor cochleovestibular developmental abnormalities could eventually lead to the progressive phenotype seen in the families