Mouse anti-Rat Kcnd2 monoclonal antibody, clone T68-2

Numerous studies and case reports show comorbidity of autism and epilepsy, suggesting some common molecular underpinnings of the two phenotypes. However, the relationship between the two, on the molecular level, remains unclear. Here, whole exome sequencing was performed on a family with identical twins affected with autism and severe, intractable seizures. A de novo variant was identified in the KCND2 gene, which encodes the Kv4.2 potassium channel. Kv4.2 is a major pore-forming subunit in somatodendritic subthreshold A-type potassium current (I-SA) channels. The de novo mutation p.Val404Met is novel and occurs at a highly conserved residue within the C-terminal end of the transmembrane helix S6 region of the ion permeation pathway. Functional analysis revealed the likely pathogenicity of the variant in that the p.Val404Met mutant construct showed significantly slowed inactivation, either by itself or after equimolar coexpression with the wild-type Kv4.2 channel construct consistent with a dominant effect. Further, the effect of the mutation on closed-state inactivation was evident in the presence of auxiliary subunits that associate with Kv4 subunits to form I-SA channels in vivo. Discovery of a functionally relevant novel de novo variant, coupled with physiological evidence that the mutant protein disrupts potassium current inactivation, strongly supports KCND2 as the causal gene for epilepsy in this family. Interaction of KCND2 with other genes implicated in autism and the role of KCND2 in synaptic plasticity provide suggestive evidence of an etiological role in autism.

Phospholamban (PLN), the reversible inhibitor of the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA2a), is a key regulator of myocyte Ca2+ cycling with a significant role in heart failure. We previously showed that the single amino acid difference between human and mouse PLN results in increased inhibition of Ca2+ cycling and cardiac remodeling and attenuated stress responses in transgenic mice expressing the human PLN (hPLN) in the null background. Here we dissect the molecular and electrophysiological processes triggered by the super-inhibitory hPLN in the mouse. Using a multidisciplinary approach, we performed global gene expression analysis, electrophysiology, and mathematical simulations on hPLN mice. We identified significant changes in a series of Na+ and K+ homeostasis genes/proteins (including Kcnd2, Scn9a, Slc8a1) and ionic conductance (including L-type Ca2+ current, Na+/Ca2+ exchanger, transient outward K+ current). Simulation analysis suggests that this electrical remodeling has a critical role in rescuing cardiac function by improving sarcoplasmic reticulum Ca2+ load and overall Ca2+ dynamics. Furthermore, multiple structural and transcription factor gene expression changes indicate an ongoing structural remodeling process, favoring hypertrophy and myogenesis while suppressing apoptosis and progression to heart failure. Our findings expand current understanding of the hPLN function and provide additional insights into the downstream implications of SERCA2a superinhibition in the mammalian heart.