Association of rare non-coding SNVs in the lung-specific FOXF1 enhancer with a mitigation of the lethal ACDMPV phenotype

Item does not contain fulltextHaploinsufficiency of FOXF1 causes alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV), a lethal neonatal lung developmental disorder. We describe two similar heterozygous CNV deletions involving the FOXF1 enhancer and re-analyze FOXF1 missense mutation, all associated with an unexpectedly mitigated disease phenotype. In one case, the deletion of the maternal allele of the FOXF1 enhancer caused pulmonary hypertension and histopathologically diagnosed MPV without the typical ACD features. In the second case, the deletion of the paternal enhancer resulted in ACDMPV rather than the expected neonatal lethality. In both cases, FOXF1 expression in lung tissue was higher than usually seen or expected in patients with similar deletions, suggesting an increased activity of the remaining allele of the enhancer. Sequencing of these alleles revealed two rare SNVs, rs150502618-A and rs79301423-T, mapping to the partially overlapping binding sites for TFAP2s and CTCF in the core region of the enhancer. Moreover, in a family with three histopathologically-diagnosed ACDMPV siblings whose missense FOXF1 mutation was inherited from the healthy non-mosaic carrier mother, we have identified a rare SNV rs28571077-A within 2-kb of the above-mentioned non-coding SNVs in the FOXF1 enhancer in the mother, that was absent in the affected newborns and 13 unrelated ACDMPV patients with CNV deletions of this genomic region. Based on the low population frequencies of these three variants, their absence in ACDMPV patients, the results of reporter assay, RNAi and EMSA experiments, and in silico predictions, we propose that the described SNVs might have acted on FOXF1 enhancer as hypermorphs

Kinesin and Dynein-Dynactin at Intersecting Microtubules: Motor Density Affects Dynein Function

Kinesin and cytoplasmic dynein are microtubule-based motor proteins that actively transport material throughout the cell. Microtubules can intersect at a variety of angles both near the nucleus and at the cell periphery, and the behavior of molecular motors at these intersections has implications for long-range transport efficiency and accuracy. To test motor function at microtubule intersections, crossovers were arranged in vitro using flow to orient successive layers of filaments. Single kinesin and cytoplasmic dynein-dynactin molecules fused with green-fluorescent protein, and artificial bead cargos decorated with multiple motors, were observed while they encountered intersections. Single kinesins tend to cross intersecting microtubules, whereas single dynein-dynactins have a more varied response. For bead cargos, kinesin motion is independent of motor number. Dynein beads with high motor numbers pause, but their actions become more varied as the motor number decreases. These results suggest that regulating the number of active dynein molecules could change a motile cargo into one that is anchored at an intersection, consistent with dynein's proposed transport and tethering functions in the cell