From page 166 of a report posted recently at Academia.edu:
Majkop verfügen sowohl über eine «paläolithische» Haplogruppe (U8) als auch über «neolithische» Haplogruppen: V (Недолужко u. a. 2014), T2, N1. Bei einem Objekt aus einem Grab bei der Staniza Novosvobodnaja fanden wir auch die Haplogruppe М52. Die gewonnenen Daten sprechen für eine (auf dem Niveau der mitochondrialen DNA) mögliche genetische Gemeinschaft der archäologischen Kulturen von Majkop und Novosvobodnaja.
The presence of Indian-specific mtDNA haplogroup M52 is surprising. Maykop territory was located just south of the steppe, but M52 isn't found in any of the Bronze and Iron Age samples from the steppe tested to date.
Here's the comment from Haak, from an abstract titled The role of the Caucasus in the formation of the Eurasia's genetic makeup: Insights and questions from ancient DNA research.
Recent genetic research on autosomal and uniparentally-inherited markers has shown a remarkable genetic uniformity of Caucasian populations despite the region’s notable linguistic and cultural diversity. When compared to neighbouring regions, the smooth genetic transition from the Near/Middle East to the Caucasus is in stark contrast to the marked differences to populations from the East European steppes. Flanked by the Black and the Caspian Seas, it remains unclear to what extent the Caucasus served as a corridor and whether and if so when ancient migrations had affected and shaped the region’s genetic profile. Ancient DNA research on Mesolithic, Neolithic and Bronze Age individuals from Western Eurasia have recently thrown fresh light on the Caucasus as region, which appears to have played a critical role in the formation of the genetic ancestry of the Yamnaya people, Bronze Age pastoralist of the east European steppes. The Yamnaya carry strong signals of eastern hunter-gatherer (EHG) ancestry and ancient Near Eastern ancestry that is different from the one that giving rise to early European farmers. While modern-day Armenians are the best proxy for the putative source population of the EHG dilution in the steppes, it is highly likely that prehistoric cultural groups from the Caucasus will provide a much better temporal and contextual fit.
Actually, I'd say western Georgians are the best proxy for the putative source population of the EHG dilution in the steppes. See here...
Yamnaya's exotic ancestry: The Kartvelian connection