Early onset or syndromic epilepsy

Gene: KATNB1

Red List (low evidence)

Assoc with AR lissencephaly 6 with microcephaly. Severe microcephaly and developmental delay and brain imaging shows variable malformations of cortical development including lissencephaly, pachygyria and hypoplasia of the corpus callosum. Epilepsy is reported in some patients.

Created: 23 Sep 2019, 1:08 p.m. | Last Modified: 23 Sep 2019, 1:08 p.m.

Panel Version: 1.336

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Comment on list classification: Updated rating from Grey to Amber, and added watchlist tag: KATNB1 was added to the panel and rated Green by Konstantinos Varvagiannis. Not yet associated with a disorder in Gene2Phenotype. Linked to lissencephaly with microcephaly in OMIM. There are sufficient cases from from the literature to support inclusion on the epilepsy panel (PMIDs:25521378, 25521379, 26640080) but epilepsy is not a feature in all cases and a Red recent review was left by Helen Lord. Therefore rated Amber as other panels may be more appropriate.

Created: 26 Sep 2019, 4:05 p.m. | Last Modified: 26 Sep 2019, 4:05 p.m.

Panel Version: 1.340

KATNB1 was added to the panel and rated Green by Konstantinos Varvagiannis. Summary of evidence is as follows (see Konstantinos Varvagiannis' review for details): 3 publications reporting patients with biallelic KATNB1 variants. The phenotype includes seizures in some, but not all cases:

PMID:25521378. Mishra-Gorur et al. 2014 report 5 families with malformations of cortical development and homozygous KATNB1 variants. In many families homozygous variants in additional genes were also reported. Epilepsy was reported in 3/7 individuals (from 2 families): Supplementary Table S1).

PMID:25521379. Hu et al., 2014 report 3 Middle Eastern families with microcephaly, Global DD and seizures, and 3 different homozygous variants in KATNB1.

PMID:26640080. Yigit el al. 2016 report a homozygous acceptor splice-site intronic KATNB1 variant in a 5 year old Turkish girl born to consanguineous cousins, who presented with congenital microcephaly, lissencephaly, short stature, polysyndactyly, dental abnormalities and developmental delay. She developed seizures age 6 months.

Created: 19 Sep 2019, 12:09 p.m. | Last Modified: 26 Sep 2019, 3:53 p.m.

Panel Version: 1.336

Green List (high evidence)

Biallelic pathogenic KATNB1 variants cause Lissencephaly 6, with microcephaly (MIM 616212). At least 13 affected individuals from 9 (mostly consanguineous) families have probably been reported in the following articles:

- Mishra-Gorur et al. (2014 - PMID: 25521378) [7 individuals from 5 unrelated families]
- Hu et al. (2014 - PMID: 25521379) [5 individuals from 3 families]
- Yigit el al. (2016 - PMID: 26640080) [1 subject born to consanguineous parents]

Seizures can be part of the phenotype (although not universal / reported in all 3 studies in several families). Several different variants have been reported to date. Extensive studies as for the impact of mutations at the cellular level as well as animal models (zebrafish, mouse, drosophila) support involvement of KATNB1. These arguments, provided mainly by the first two studies, are summarized in the respective OMIM entry for the disorder : https://omim.org/entry/616212 (variants and their effect are discussed in the entry for KATNB1 - https://omim.org/entry/602703)

The individual reported by Yigit el al. was a 5 year-old girl with - among others - severely delayed psychomotor development and seizures. The child was found to harbor a homozygous splice site variant (removing the acceptor AG signature). Confirmation of the variant and segregation studies were performed with Sanger sequencing. cDNA studies were carried out and demonstrated aberrant splicing.

KATNB1 is not associated with any disorder in G2P.
The gene is included in panels for ID offered by several diagnostic laboratories (incl. Radboudumc).

As a result, this gene can be considered for inclusion in the current panel probably as green (or amber).
Sources: Literature

Created: 31 Aug 2019, 10:58 a.m.

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
Lissencephaly 6, with microcephaly (MIM 616212)

Publications

• 25521378
• 25521379
• 26640080